PHYSIOLOGY 

BRIEFER  COURSE 


GOLTON 


BIOLOGY 

LIBRARY 

G 


.wt 


X-RAY    PHOTOGRAPH    OF   HAND 

SHOWING  SHOT  CARRIED   FOR  TWENTY  YEARS 

(From  Recreation,  by  permission  of  G.  O.  Shields.) 


BRIEFER    COURSE 


PHYSIOLOGY 


ILLUSTRATED  BY  EXPERIMENT 


BY 


BUEL    P.    COLTON,    A.M. 

AUTHOR   OF   "  PHYSIOLOGY,  EXPERIMENTAL  AND    DESCRIPTIVE 

"PRACTICAL  ZOOLOGY";    AND   PROFESSOR   OF  NATURAL 

SCIENCE  IN  THE   ILLINOIS  STATE   NORMAL 

UNIVERSITY 


BOSTON,  U.S.A. 

D.  C.  HEATH   &  CO.,  PUBLISHERS 
1900 


BIOLOGY 

LIBRARY 

G 


COPYRIGHT,  1899, 
BY  BUEL  P.  COLTON. 


Nortooob 

J.  S.  Gushing  &  Co.  -  Berwick  &  Smith 
Norwood  Mass.  U.S.A. 


PREFACE. 


THE  author's  "  Experimental  and  Descriptive  Physiol- 
ogy" has  been  adopted  by  a  large  number  of  schools  and 
colleges.  But  there  are  many  schools  in  which,  owing  to 
the  youth  of  the  pupils,  the  shortness  of  the  time  allotted  to 
the  subject,  or  the  meagerness  of  laboratory  facilities,  such 
a  rigorous  course  cannot  be  taken.  For  such  schools  this 
simpler  book  is  written.  While  it  contains  considerably 
less  experiment  and  dissection  than  the  larger  book,  it  is 
still  based  upon  experimental  work.  No  teaching  of  physi- 
.  ology  is  worthy  of  the  name  unless  it  rests  upon  experi- 
ment, observation,  and  dissection.  The  ridiculous  answers 
of  the  pupil  who  has  learned  mere  "book  physiology" 
furnish  the  standard  jest  of  the  educational  journal.  Try- 
ing to  teach  physiology  without  experiment  is  not  only  in 
opposition  to  modern  views  of  pedagogy  and  psychology, 
but  it  is  equally  at  variance  with  the  common  sense  of  the 
business  man's  view.  Such  teaching  is  a  mere  mummery 
of  words — it  teaches  neither  how  to  know  nor  to  do. 

In  fitting  this  work  for  the  less  mature  mind,  special 
attention  has  been  paid  to  conciseness  and  brevity  of  state- 
ment and  to  clearness  of  exposition.  Sentences  and  para- 

iii 

735021 


iv  PR  El- ACE. 

graphs  have  been  made  short;  chapters  are  short,  with 
definite  summaries  appended. 

Function,  rather  than  structure,  has  been  made  promi- 
nent. Only  so  much  of  anatomy  as  is  really  needed  to 
understand  the  working  of  the  organs  has  been  introduced. 
The  experimental  work  and  directions  for  dissection,  as 
well  as  some  of  the  more  difficult  points,  have  been  put  in 
smaller  type,  so  they  may  more  readily  be  omitted  where 
it  is  not  possible  to  complete  all  the  work  in  the  given 
time. 

Although  hygiene  has  been  given  a  prominent  place, 
yet  it  may  be  claimed  that  when  the  pupil  is  well  grounded 
in  the  functions  of  the  different  organs,  from  observational 
and  experimental  work,  many  of  the  rules  of  hygiene  will 
readily  occur  to  him  as  natural  inferences.  When  other 
rules  for  the  preservation  of  health,  which  might  not  occur 
to  him,  are  suggested,  he  will  see  their  significance  because 
he  understands  the  underlying  principle ;  and  he  not  only 
can,  but  will,  obey  the  rule  better  because  he  sees  reason 
in  it,  and  does  not  follow  it  blindly  as  an  arbitrary  law 
thrust  upon  him.  Questions  are  given,  at  the  end  of  each 
chapter,  to  test  the  pupil's  knowledge  of  principles  by 
application  to  new  cases. 

Some  of  the  more  desirable  reforms  in  nomenclature  have 
been  adopted ;  among  these  are  the  use  of  the  terms  ante- 
rior, meaning  toward  the  head ;  posterior,  in  the  opposite 
direction ;  dorsal,  toward  the  back ;  ventral,  toward  the 
region  of  the  belly.  These  terms,  used  instead  of  "  up  " 


PREFACE.  V 

and  "down,"  "front"  and  "back,"  will  do  away  with 
much  confusion,  especially  since  we  are  obliged  to  use  the 
structure  of  horizontal-bodied  animals  to  illustrate  human 
anatomy.  Many  Latin  terms,  such  as  "vena  cava"  should 
be  replaced  by  English,  as  caval  vein.  Postcaval  vein  and 
precaval  vein  are  easier  and  better  than  "  vena  cava  infe- 
rior "  and  "vena  cava  superior."  In  many  cases  the 
English  plural  may  well  replace  the  Greek  or  Latin  form, 
as  ganglion,  plural  ganglions.  Blood  tube  is  better  than 
"bloodvessel."  The  best  authorities  say  spinal  bulb  in- 
stead of  the  long  "medulla  oblongata."  Food  tube  is 
simpler  than  "  alimentary  canal,"  especially  as  the  tube  is 
not  canal-like.  The  rib-bearing  vertebras  are  thoracic,  and 
are  no  more  "dorsal"  than  the  other  parts  of  the  spinal 
column. 

Effort  has  been  made  to  lay  stress  on  the  more  impor- 
tant topics,  and  the  skeleton  is  relegated  to  a  subsidiary 
place,  as  a  knowledge  of  it  has  so  little  to  do  with  practical 
hygiene.  The  heart  and  the  stomach  receive  full  treat- 
ment, while  matters  of  such  slight  importance  as  the  hair 
and  nails  are  briefly  dismissed. 

The  order  of  topics  is  the  result  of  long  experience. 
For  many  years  the  author  has  sought  to  find  the  most 
natural  sequence  of  subjects,  so  that,  as  the  work  pro- 
gressed, the  pupil  would  find  the  way  best  prepared  for 
him.  Without  claiming  that  this  is  the  best  sequence,  the 
writer  is  sure  that  it  is  the  "  path  of  least  resistance." 

The  subject  of  Alcohol  has  been  treated  in  full  com- 


vi  PREFACE. 

pliance  with  the  law.  Copious  quotations  have  been  taken 
from  the  best  authorities  on  this  subject.  The  same 
high-grade  illustrations  have  been  used  that  brought  such 
favorable  comment  on  the  earlier  work. 

This  briefer  edition  has,  too,  the  full  benefit  of  the 
criticism  of  the  eminent  authorities  whose  names  are  listed 
in  the  larger  work. 

TO   THE   TEACHER. 

For  any  practical  work  in  physiology  it  is  very  desirable 
to  have  a  room  furnished  with  tables  and  supplied  with 
water. 

Each  pupil  should  make  full  notes  and  drawings  of  the 
work  done  and  the  organs  studied  and  dissected.  Only  by 
so  doing  will  he  firmly  fix  and  retain  what  he  gathers  from 
day  to  day. 

In  the  larger  work  by  the  author  are  many  experiments 
and  dissections  given  in  full  which  are  here  omitted  in 
order  to  present  a  briefer  course.  In  the  larger  work  there 
is  also  given  a  list  of  books  which  are  most  helpful  in 
teaching  physiology. 


CONTENTS. 


CHAPTER   I. 

PAGE 

INTRODUCTION •        l 

Health.  Care  of  the  Body.  Hygiene.  Physiology.  Organ.  Func- 
tion. Anatomy.  Tissues.  Cells.  Physiological  Division  of  Labor. 

CHAPTER   II. 

MOTION 7 

Motion  Necessary  to  Life.  Experiments  with  our  Muscles.  Action 
of  Muscle.  Structure  of  Muscle.  Connective  Tissue.  Laws  of 
Muscle  Action.  Flexors  and  Extensors.  Symmetry.  Muscles  and 
Bones.  Levers.  Locomotion.  Uses  of  Bones. 

CHAPTER  III. 

THE  GENERAL   FUNCTIONS   OF  THE  NERVOUS   SYSTEM  —  SENSATION 

AND.  MOTION 24 

Muscles  controlled  by  Nerves.  Voluntary  and  Involuntary  Motion. 
The  Spinal  Cord.  The  Spinal  Nerves.  Structure  of  Nerves. 
Function  of  Nerves.  Structure  of  the  Spinal  Cord.  Ganglions. 
Reflex  Action  of  the  Spinal  Cord.  Reflex  Action  of  the  Spinal 
Cord  in  the  Frog.  Function  of  the  Nerve  Roots.  Importance  of 
Reflex  Action.  Inhibition.  Nature  of  a  Nervous  Impulse.  Har- 
mony in  Muscle  Action.  Nerves  depend  on  Blood  Supply. 

CHAPTER   IV. 

CIRCULATION  OF  THE  BLOOD 39 

The  Blood  and  its  Work.  The  Rate  of  the  Heart  Beat.  Position 
and  Size  of  the  Heart.  The  Valves  of  the  Heart.  The  Blood 
Tubes  Connected  with  the  Heart.  The  Action  of  the  Heart.  Work 
and  Rest  of  the  Heart.  Action  of  the  Large  Arteries.  Variation 
in  Blood  Supply.  Plain  Muscle  Fibers  in  the  Walls  of  the  Arteries. 

vii 


viii  CONTENTS. 

I'AGK 

Circulation  of  Blood  in  the  \Yel>  of  the  Frog's  Foot.  Blood  Mow  in 
the  Capillaries.  The  Veins.  The  Valves  in  the  Veins.  F.t'fect  of 
Pressure  on  the  Veins.  Rate  of  Blood  Flow.  Nourishment  of  the 
Walls  of  the  Heart.  Effect  of  Gravity  on  Circulation. 

CHAPTER  V. 

CONTROL  OF  CIRCULATION.  —  THE  BLOOD  AND  THE  LYMPH  ....  64 
The  Effect  of  Emotions  on  Circulation.  Rhythmic  Action  of  the 
Heart.  Nerve  Control  of  the  Heart.  Sympathetic  Nervous  System. 
The  Vagus  Nerve.  Inhibition.  Vaso-motor  Nerves.  Blushing. 
Regulation  of  the  Size  of  the  Arteries.  Effect  of  Exercise  on  the 
Size  of  the  Arteries.  Effects  of  Alcohol  on  Circulation.  The 
Bloocl.  The  Corpuscles  of  the  Blood.  The  Plasma.  Hemoglobin. 
Coagulation  of  Blood.  Fibrin.  Amount  of  Blood.  Distribution  of 
Blood.  The  Lymph  Spaces.  Lymph  Tubes.  Lymphatic  Glands. 
Flow  of  Lymph.  Massage.  Transfusion  of  Blood. 

CHAPTER   VI. 

RESPIRATION 84 

The  Close  Relation  between  Circulation  and  Respiration.  Organs 
of  Respiration.  Structure  of  the  Lungs.  The  Windpipe.  Cilia. 
The  Pleura.  The  Diaphragm.  Action  of  the  Diaphragm.  Move- 
ments of  Respiration.  Forces  of  Inspiration.  Resistances  to  Inspi- 
ration. Elastic  Reactions  of  Expiration.  Forced  Respiration.  Rate 
of  Respiration.  Modifications  of  Respiration.  Lung  Capacity. 
Hygiene  of  Respiration.  Breathing  through  the  Mouth.  Control 
of  Respiration.  Chemistry  of  Respiration.  Composition  of  the 
Air.  Exchanges  between  the  Air  and  the  Blood  in  the  Lungs. 
Oxyhemoglobin.  The  Gases  in  the  Blood.  Production  of  Heat 
and  Motion  in  the  Body.  Oxidation  of  Live  Tissues.  Body  and 
Locomotive  Compared.  Storage  of  Oxygen  in  the  Tissues.  Re- 
breathing  Air. 

CHAPTER    VII. 

VENTILATION  AND  HEATING. — DIST  AND  BACTERIA 114 

Need  of  Ventilation.  Grates.  Principles  of  Ventilation.  Stoves. 
Furnaces.  Foul-air  Shafts  and  Fans.  Steam  and  Hot-water 
Heating.  Direct  and  Indirect  Heating.  Dead  Dust.  Sources  of 
Dust.  Live  Dust.  Consumption.  Disease  Germs.  Bacteria.  How 
to  avoid  Dust.  Sweeping.  Contagious  Diseases.  Putrefaction. 
Preservation  of  Foods.  Need  of  Removal  of  Waste. 


CONTENTS.  ix 

CHAPTER   VIII. 

PAGE 

EXCRETION 130 

The  Skin  throws  off  Perspiration.  The  Structure  of  the  Skin.  The 
Epidermis.  Color  of  the  Skin.  The  Dermis.  Sweat  Glands.  Es- 
sentials of  a  Gland.  Blood  Supply  of  Glands.  Oil  Glands. 
Composition  of  Sweat.  Amount  of  Perspiration.  Functions  of  the 
Skin.  Regulation  of  Bodily  Temperature  by  the  Skin.  Distribu- 
tion of  Heat  in  the  Body.  Regulation  of  Bodily  Temperature  by 
Food  and  Clothing.  The  Kidneys.  Work  of  the  Kidneys.  Rela- 
tion of  the  Skin  and  Kidneys. 

CHAPTER    IX. 

Foons  AND  COOKING 144 

Necessity  of  Food.  Food  Defined.  Foodstuffs.  Proteids.  Impor- 
tance of  Proteids.  Meat.  Fish.  Eggs.  Milk.  Cheese.  Vege- 
table Proteids.  Carbohydrates.  Grains.  Wheat.  Corn.  Rice. 
Oats.  Potatoes.  Vegetables.  Fruits.  Water.  Impurities  in 
Water.  Typhoid  Fever.  Ice-water.  Boiling  Water.  Salts. 
Necessity  of  a  Mixed  Diet.  Effects  of  Cold  on  Appetite  for  Fats. 
Vegetarians.  Tea.  Coffee.  Beef  Tea.  Cooking.  Soups. 

CHAPTER   X. 
THE  DIGESTIVE  SYSTEM 159 

The  Object  of  Food.  The  Digestive  Tube.  Organs  of  Digestion. 
The  Mouth.  The  Teeth  —  Kinds,  Structure,  Arrangement.  Care 
of  the  Teeth.  Salivary  Glands.  Action  of  Salivary  Glands.  Saliva 
and  its  Uses.  Mucus  and  Mucous  Glands.  The  Pharynx.  Swal- 
lowing. The  Gullet.  The  Structure  of  the  Stomach.  Gastric 
Glands.  Blood  Supply  of  the  Stomach.  Stomach  Digestion. 
Churning  Action  of  the  Stomach.  Time  of  Stomach  Digestion. 
Chyme.  Absorption  from  the  Stomach.  The  Intestine.  The 
Liver.  The  Pancreas.  Bile.  Pancreatic  Juice.  The  Portal  Circu- 
lation. Functions  of  the  Bile.  Work  of  the  Pancreatic  Juice. 
Intestinal  Juice. 

CHAPTER   XL 

ABSORPTION  —  DIGESTION  COMPLETED 181 

Absorption.  Villi.  Routes  of  Different  Foods  after  Absorption.  Dif- 
fusion and  Osmosis.  Absorption  a  Vital  Process.  The  Lacteals 
and  the  Lymphatics.  Outline  of  Digestion.  The  Colon.  Work 
of  the  Large  Intestine.  Constipation.  Laxative  and  Constipating 


X  CONTENTS. 

PAGE 

Foods.  Hygiene  of  Digestion.  Deliberation  in  Eating.  Thorough 
Mastication.  Fleets  of  Repose  on  Digestion.  Conversation  at 
Meals.  Value  of  Soups  and  Desserts.  Hot  Drink  at  Meals.  Time 
of  Meals.  Eating  between  Meals.  Amount  of  Food  Needed. 
Errors  in  Diet. 

CHAPTER   XII. 

NUTRITION 195 

Ledger  Account  of  the  Body  and  its  Organs.  Blood  a  Mixture  of 
Good  and  Bad.  Action  of  Diseased  Kidneys.  Blood  Stream  like 
Water  Pipes  and  Sewer  Combined.  A  Living  Eddy.  Importance 
of  Renewal  of  Blood  and  Lymph.  Fat  as  a  Tissue.  Hibernation. 
Respiration  and  Oxidation  of  Candle.  Glycogen.  Muscular  Exer- 
tion and  Excretion  of  Urea.  Metabolism.  Indestructibility  of 
Matter.  Indestructibility  of  Force.  Utilization  of  Energy  in  the 
Body  and  in  Machines.  Correlation  and  Conservation  of  Energy. 

CHAPTER   XIII. 

ALCOHOL 208 

Alcohol  and  Crime.  Alcohol  and  Energy.  Alcohol  and  Heat.  Alco- 
hol and  Muscular  Energy.  Arctic  Explorers.  Alcohol  and  Train- 
ing. Stimulants.  Narcotics.  Temperance  Drinks.  Testimony  of 
Physiologists.  Testimony  of  Army  Officers.  Testimony  of  a  Natu- 
ralist. Physiological  Effects  of  Alcohol. 

CHAPTER  XIV. 

EXERCISE  AND  BATHING 226 

How  Exercise  is  Beneficial.  Exercise  for  General  Health.  Nature's 
Rewards  and  Punishments.  Exercise  prolongs  Life.  Choice  of 
Exercise.  Games  of  School  Children.  Tennis.  Baseball  and 
Football.  Boxing.  Bicycling.  Exercise  for  Middle-aged  Men. 
Taking  Cold.  Diarrhea.  Bathing.  Cold  Baths.  Bath  Mits.  Time 
for  Bathing.  Warm  Baths  vs.  Cold  Baths.  Exercise  Arterial  Mus- 
cles. Habit  of  Cold  Bathing  acquired  gradually. 

CHAPTER   XV. 

THE  BRAIN 235 

The  Coverings  of  the  Brain.  Parts  of  the  Brain.  The  Cerebrum. 
The  Cerebellum.  '  The  Spinal  Bulb.  Brain  of  a  Cat  or  Rabbit. 
Cranial  Nerves  and  their  Functions.  Hemispheres  of  the  Cerebrum. 
Brain  Convolutions  and  Intelligence.  Gray  and  White  Matter  of 
the  Brain.  Neuroglia.  Functions  of  the  Cerebrum.  Pigeon 
with  Cerebrum  Removed.  Functions  of  Cerebral  Cortex.  Center 


CONTENTS.  xi 

PAGE 

of  Sensations  itself  Insensible.  Crossed  Control  of  the  Body.  Lo- 
cation of  Brain  Functions.  Left  Hemisphere  better  Developed. 
Location  of  Sensation  Centers.  Brain  Work  and  Brain  Rest. 
Sleeplessness.  Fatigue.  Control  of  Mind.  Habit  of  Resting  the 
Brain.  Nervous  Tissues  least  Affected  by  Starvation.  Blood  Supply 
of  the  Brain.  Fainting.  Apoplexy.  Meningitis.  The  Water 
Cushion  of  the  Brain.  Relative  Activity  of  Gray  and  White  Matter. 

CHAPTER   XVI. 

EFFECTS  OF  ALCOHOL  ON  THE  NERVOUS  SYSTEM 250 

The  Chief  Effect  of  Alcohol  is  on  the  Nervous  System.  Inebriety  re-" 
garded  as  a  Disease.  Moral  Deterioration  produced  by  Alcohol. 
Narcotics.  Opium.  Cocaine.  Chloral  Hydrate.  Chloroform. 
Tobacco.  Cigarette  Smoking. 

CHAPTER  XVII. 

GENERAL  CONSIDERATIONS  CONCERNING  THE  NERVOUS  SYSTEM  .  .  .  261 
Nerve  Stimuli.  Kinds  of  Nerve  Stimuli.  Essential  Similarity  of  All 
Nerve  Fibers.  Relation  of  Stimulus  and  Sensation.  Reaction 
Time.  Reflex  Action.  Connection  of  Brain  'Centers.  Nature  of 
Sensation.  Subjective  Sensations.  The  Relative  Nature  of  Sensa- 
tion. Induction  Currents  used  in  Physiological  Experiments. 
Dreams.  Lingering  Effect  of  Sensations.  Habits  are  Acquired 
Reflex  Actions.  Usefulness  of  Resting.  Nervous  System  vs.  Tele- 
graph System.  Efferent  Currents.  Afferent  Currents. 

CHAPTER   XVIII. 

THE  GENERAL  SENSES 271 

The  Body  a  Collection  of  Organs.  Influence  from  the  External  World. 
Classification  of  the  Senses.  General  Sensations  and  Special  Senses. 
The  Muscular  Sense.  Importance  of  Muscular  Sense.  Dependence 
of  Sight  on  Muscular  Sense  and  Touch.  Pain.  Pain  a  General 
Sense.  Extent  of  Pain.  Use  of  Pain.  Hunger  and  Thirst. 

CHAPTER   XIX. 

THE  SPECIAL  SENSES  —  TOUCH  AND  TEMPERATURE  SENSE  ....  278 
What  we  learn  by  Touching  Objects.  Cutaneous  Sensations.  Nerve 
Endings  in  the  Skin.  Touch  Corpuscles.  Touch  the  most  General 
of  the  Senses.  Pressure  Sense.  Local  Sign.  Test  by  Compass 
Points.  Reference  of  Sensation  to  the  Region  of  the  Nerve  End- 
ings. Temperature  Sense. 


xil  CONTEWS. 

CHAPTKR   XX. 

PAGE 

THE  SENSE  OF  SIGHT 285 

Protection  of  the  Eye.  The  Lacrymal  Secretion.  External  Parts  of 
the  Eye.  The  Conjunctiva.  Muscles  of  the  Eyeball.  Movements 
of  the  Eye.  Coats  of  the  Eye.  The  Sclerotic  Coat.  The  Choroid 
Coat.  The  Retina.  The  Cornea.  The  Iris.  The  Pupil.  Regula- 
tion of  the  Amount  of  Light  admitted  into  the  Eye.  The  Refract- 
ing Media  of  the  Eye.  The  Aqueous  Humor.  The  Vitreous  Humor. 
The  Crystalline  Lens.  The  Lens  Capsule.  The  Hyaloid  Mem- 
brane. The  Ciliary  Muscle.  Inversion  of  the  Image.  Adjustment 
for  Distance.  Action  of  the  Ciliary  Muscle.  Defects  of  Eyesight. 
Structure  of  the  Retina.  Importance  of  the  Retina.  The  Blind 
Spot.  The  Optic  Nerve  not  Sensitive  to  Light.  Sympathy  between 
the  Eyes.  Pain  in  the  Eyes.  Color  Sensations.  Color  Blindness. 
Stereoscopic  Vision.  After-images.  Care  of  the  Eyes. 

CHAPTER   XXI. 

TASTE,  SMELL,  AND  HEARING ^01 

Uses  of  the  Sense  of  Taste.  The  Papilla;.  Nerve  Supply  of  the 
Tongue.  Solution  Necessary  for  Tasting.  Flavors.  Effect  of 
Temperature  on  Taste.  The  Sense  of  Smell.  Why  we  Sniff.  The 
Sense  of  Bearing.  The  External  Ear.  The  Tympanum.  The 
Middle  Ear.  The  Eustachian  Tube.  The  Internal  Ear.  The  Pro- 
duction of  Sound.  The  Equilibrium  Sense.  The  Care  of  the  Far. 
The  Use  of  the  Ears. 

CHAPTER   XXII. 
THE  VOICE 309 

The  Ear  and  the  Voice.  What  we  can  learn  from  our  own  Throats. 
The  Vocal  Cords.  Reinforcement  of  Sound.  Pitch  and  Voice. 
Voice  and  Speech.  Vowels  and  Consonants.  Difference  between 
Voices.  Hoarseness.  Whispering.  Culture  of  the  Voice. 

CHAPTER   XXIII. 

ACCIDENTS.  —  WHAT  TO  DO  TILL  THE  DOCTOR  COMES 314 

How  to  stop  Flow  of  Blood  from  Arteries.  Bleeding  from  the  Upper 
Arm.  Bleeding  from  the  Neck.  Wounds  in  the  Thigh.  Bleeding 
from  Veins.  Hemorrhage  of  the  Lungs  or  Stomach.  Bleeding  from 
the  Nose.  Treatment  of  Burns.  Danger  from  Burning  Clothing. 


CONTENTS.  xiii 


Treatment  of  Fainting.  Broken  Bones.  Sunstroke.  Treatment  of 
the  Drowned.  Swimming.  Suffoeation  in  Wells.  Bites  of  Cats, 
Dogs,  etc.  Wounds  from  Thorns,  Rusty  Nails,  etc.  Snake  Bites. 
Poisons  and  their  Antidotes.  Poison  Ivy.  The  Sick-room.  Qual- 
ities of  the  Nurse.  Care  of  the  Sick. 

CHAPTER   XXIV. 

THE  SKELETON 330 

Axial  Skeleton.  Appendicular  Skeleton.  Uses  of  the  Bones.  Study 
of  a  Vertebra.  Table  of  the  Bones.  The  Spinal  Column.  Articu- 
lations of  a  Vertebra.  The  Cervical  Vertebras.  Atlas  and  Axis. 
The  Thoracic  Vertebras.  The  Lumbar  Vertebras.  The  Sacrum  and 
the  Coccyx.  Flexibility  of  the  Spinal  Column.  Curves  of  the  Spinal 
Column.  Cavities  of  the  Skeleton.  Pronation  and  Supination. 
Weight  of  the  Bones.  Microscopic  Structure  of  Bone.  Classifica- 
tion of  Joints.  Sprains  and  Dislocations. 

CHAPTER   XXV. 

THE  MUSCLES 341 

The  Number  of  Muscles.  The  Arrangement  of  Muscles.  Forms  of 
Muscles.  Names  of  Muscles.  Peculiar  Muscles.  Heart  Muscle. 
Three  kinds  of  Muscular  Fiber  Compared.  Each  Fiber  a  Cell. 
Muscles  of  Expression.  Muscles  and  Fat.  Convulsions.  Rigor 
Mortis.  Some  Prominent  Muscles.  Sculpture  and  Anatomy. 


APPENDIX    .     . 347 

Antidotes.     Disinfectants.     Vital  Statistics. 

GLOSSARY 360 

INDEX ....  371 


PHYSIOLOGY. 


CMA.P,TER    I.    ,'••.:: 


Health.  —  Is  it  not  a  splendid  thing  to  be  well  and 
strong  ?  To  be  full  of  bounding  health  ?  To  "  feel  one's 
life  in  every  limb  "  ? 

Who  does  not  desire  to  prolong,  so  far  as  possible,  this 
condition  characteristic  of  youth  ? 

Natural  and  Artificial  Modes  of  Life.  —  An  animal 
living  in  a  state  of  nature  may  keep  well  and  live  its 
natural  period  of  life  without  knowing  anything  about  the 
laws  of  health.  But  as  students  or  indoor  workers,  many 
of  us  lead  a  sedentary  life  ;  we  are  not  natural,  but  often 
highly  artificial,  in  our  mode  of  living.  We  move  about 
but  little,  whereas  the  animal  abounds  in  motion.  We 
concentrate  energy  upon  mental  effort,  thus  diverting  a 
large  share  of  our  sum  total  of  energy  away  from  the  pro- 
cess of  nutrition.  We  often  shut  ourselves  in  rooms  nearly 
air-tight.  We  eat  poorly  chosen  and  ill-prepared  food. 
We  devour  it  hastily,  often  when  we  are  not  in  fit  con- 
dition to  take  food.  In  short,  we  frequently  disobey  the 
laws  of  Nature.  Now,  Nature  punishes  every  violation  of 
her  laws.  She  never  forgives,  never  forgets. 

1 


Value  of  Knowledge. — The  out-of-door  worker  may 
not  suffer  so  much  from  ignorance  in  these  matters. 
From  the  character  of  his  occupation,  he  is,  »to  a  certain 
•extent,  obliged  to  obey  Nature.  He  gets  enough  fresh 
air.  His  bodily  exertion  generally  brings  a  hearty  appe- 
tite, vigorous  digestion,  active  circulation  of  the  blood. 
Still,  he  would  greatly  profit  by  knowing  something  of  the 
nature  of  his  food,  its  wholesomeness  or  unwholesomeness. 
The  fact  that  he  has  fair  health  is  no  proof  that  he  always 
does  the  best  thing.  His  natural  mode  of  life  may  keep 
him  in  tolerably  good  condition  in  spite  of  his  violation  of 
certain  laws  V  b#t  ^(f  J-coldd  :uXidpubtedly  learn  how  to 
economize  in  the  purchase,  preparation,  and  proper  com- 
bination of  foods. 

Importance  of  the  Care  of  the  Body.  —  Any  machine 
of  man's  invention  must  be  kept  in  good  running  order  if 
we  would  have  it  do  good  work,  or  last  long.  We  must 
keep  a  machine  clean,  well  oiled,  and  not  overtax  it.  Are 
not  our  bodies  worth  equal  care  ?  If  some  part  of  a  ma- 
chine is  broken,  we  may  replace  it  at  moderate  expense ; 
but  none  of  the  vital  organs  can  be  replaced.  We  may 
get  a  new  mainspring  for  a  watch,  but  we  cannot  obtain  a 
new  stomach  or  lungs. 

Its  Admirable  Mechanism.  —  Aside  from  the  above 
considerations  the  human  body  is  worthy  of  study  for  its 
own  sake.  Viewed  simply  as  a  mechanism,  it  is  wonder- 
ful. Each  organ  is  so  well  adapted  to  its  work,  and  all 
the  organs  work  so  harmoniously  through  their  connection 
and  control  by  the  nervous  system,  that  we  never  cease  to 
admire  it.  We  admire  a  doll,  or  other  toy,  so  ingeniously 
constructed  that  it  can  move  its  eyes  or  walk  a  short  time 
after  being  wound  up.  But  this  live  mechanism,  which  is 


INTRODUCTION.  3 

self-winding,   self-regulating,    self-repairing,    self-directing, 
amazes  us. 

Hygiene.  —  We  take  up  the  study  of  the  human  body 
mainly  that  we  may  learn  how  to  preserve  health  ;  the 
science  of  health  is  hygiene. 

Physiology.  —  In  order  to  keep  the  various  organs  in 
good  order  we  must  know  what  their  natural  work  is,  and 
how  they  do  it ;  the  science  of  the  action  of  the  body  and 
its  parts  is  physiology. 

Organ.  —  Any  part,  or  member,  of  the  body,  which  has 
a  special  work  to  do,  is  called  an  organ,  as  the  hand,  the 
eye,  or  the  stomach. 

Function.  --  The  work,  or  action,  of  each  organ  is 
its  function. 

Anatomy.  —  In  order  to  understand  the  working  of 
each  organ  it  is  usually  necessary  to  know  something 
of  its  construction ;  the  science  of  structure  is  anatomy. 
We  do  not  need  to  go  far  into  anatomy  to  obtain  a  fail- 
knowledge  of  the  manner  in  which  our  organs  do  their 
work.  The  surgeon,  of  course,  must  be  able  to  locate 
accurately  the  various  blood  tubes,  nerves,  muscles,  etc. 
We  need  to  know  only  the  general  structure  of  the  body 
and,  more  in  detail,  some  of  the  more  important  organs, 
such  as  the  heart,  the  lungs,  the  larynx,  the  eye,  etc. 
It  is  fortunate  for  us  that  these  organs  in  the  sheep,  pig, 
and  cow  are  so  nearly  like  our  own  that  they  serve 
admirably  to  enable  us  to  understand  ourselves. 

Tissues.  —  Every  organ  is  composed  of  several  different 
kinds  of  material.  For  instance,  in  a  slice  across  a  ham 
we  see  the  skin  on  the  outside,  then  fat,  lean,  and  bone. 


4  I'HYSIOLOGY. 

These  "primary  building  materials"  of  the  body  we  call 
tissues.  A  tissue  may  be  defined  as  an  aggregation  of 
similar  cells  devoted  to  a  common  work. 

Cells. — The  whole  body  is  made  up  of  small  parts 
called  cells,  comparable  to  the  bricks  in  a  house.  These 
cells  are  of  various  shapes  in  the  different  tissues. 

In  the  more  active  tissues  the  cells  are  alive,  and  each 
cell  may  be  compared  to  the  ameba,  a  little  mass  of  living 
jelly-like  substance  called  protoplasm.  The  ameba  is  a 
protozoan  often  found  in  the  slime  at  bottom  of  stagnant 
water.  Within  this  is  a  small,  rounded  part  called  the 
nucleus.  Most  of  the  cells  of  the  body  differ  from 
the  ameba  in  having  a  distinct 
outer  covering  or  cell  wall.  A  grape 
serves  very  well  to  show  what  a  cell 
is  like.  The  whole  body  is  built  up 
Nucleus.  °f  cells,  few  of  them  large  enough 

Fig.  i.  Epithelial  Ceils  from       to    be    seen    by    the    naked    eye. 
Although    the     cells     are     closely 

packed  together,  each  cell  leads,  in  one  sense,  an  inde- 
pendent life.  But  all  work  together  to  maintain  the  life 
of  the  body.  The  cell  is  like  the  individual  in  a  com- 
munity. Each  lives  primarily  for  itself,  yet  all  work 
together  for  the  good  of  the  whole. 

Epithelial  Cells  from  the  Inside  of  the  Cheek.  —  With  the  blade  of 
a  very  dull  knife,  or  the  handle  of  a  scalpel,  gently  scrape  the  inside  of 
the  cheek.  Place  a  little  of  the  white  scraping  on  a  slide  in  a  drop 
of  water,  cover  with  a  cover  slip,  and  examine  under  a  quarter-inch 
objective.  Many  cells  will  be  seen,  some  of  them  showing  nuclei. 
Compare  these  cells  with  the  accompanying  figure. 

The  Physiological  Division  of  Labor.  —  We  are  aware 
of  the  advantages  of  division  of  labor  in  a  community.  If 


INTRODUCTION.  5 

each  person  learns  to  do  one  thing  well,  all  together  work 
economically  for  the  common  good,  time  is  saved,  and 
better  goods  are  produced.  In  the  body  there  is  a  division 
of  labor  similar  to  that  of  a  community.  Each  organ  has 
its  own  work  to  do,  and  all  work  together  for  the  common 
welfare.  The  cells  of  each  tissue  have  certain  properties 
and  peculiarities  of  form  differing  from  the  form  and 
properties  of  the  cells  of  any  other  tissue.  While  the 
general  structure  of  all  cells  is  essentially  the  same,  and 
while  they  all  have  certain  properties  in  common,  each  has 
some  one  kind  of  work  that  it  can  do  well,  and  to  which 
work  it  devotes  itself.  The  nerve  cells  receive  impressions 
from  the  outer  world,  carry  nervous  impulses,  and  control 
the  various  activities  of  the  body.  The  muscle  cells  have 
as  their  work  the  production  of  motion.  All  the  cells 
must  take  food  for  themselves  and  grow.  Each  has  a 
birth,  life,  and  death,  as  each  individual  in  a  community 
of  men ;  and  as  the  community  endures,  while  the  indi- 
vidual members  are  continually  changing,  so,  in  the  body, 
while  the  form  remains  about  the  same  from  year  to  year, 
the  cells  are  continually  changing,  some  dying,  and  others 
taking  their  places.  . 

In  an  animal  of  a  single  cell,  like  the  ameba,  the  one 
cell  must  do  everything  for  itself.  The  higher  animals  all 
begin  their  individual  life  as  an  egg,  which  is,  in  fact,  a 
single  minute  cell.  This  grows  and  divides,  forming  two 
cells.  By  repeated  division  there  accumulates  a  mass 
of  cells.  These  take  on  the  arrangement  peculiar  to  the 
kind  of  animal  from  which  the  egg  came.  But  as  the  cells 
increase  in  number  one  group  of  cells  takes  up  one  part 
of  the  work  of  .the  body,  other  cells  another  part  of  the 
work,  and  so  on. 

In  studying  history  (sociology)  we  have  to  deal  with  the 


6  J'HYSIOLOGY. 

individual,  the  community,  the  state,  and  the  nation.  The 
cell  is  an  individual,  the  community  is  a  tissue,  the  state  is 
an  organ,  and  the  nation  is  one  body. 

Let  us  proceed  to  study  the  nature  of  the  individual  cell, 
and  the  combined  actions  of  these  individuals  in  that  com- 
munity called  the  human  body. 


Summary.  —  i.    Health  is  essential  to  comfort   and   efficiency  in 
work. 

2.  Our  artificial  mode  of  life  is  at  variance  with  nature's  laws. 

3.  Only  by  obeying  the  laws  of  nature  can  we  preserve  health. 

4.  We  should  learn  these  laws  of  nature  from  the  advice  and  ex- 
perience of  others,  and  not  by  the  expensive  process  of  suffering  from 
disobedience. 

5.  Anatomy  is  the  science  of  structure.     Human  anatomy  is  the 
science  of  the  structure  of  the  human  body. 

6.  Physiology  is  the  science  of  function. 

7.  Hygiene  is  the  art  of  preserving  health. 

8.  Cells  are  the  units  of  structure  in  the  body. 

9.  A  tissue  is  a  group  of  similar  cells  having  a  single  function. 

10.  An  organ  is  a  part  having  a  special  work  or  function.     The 
organs  work  together  for  the  common  good  of  the  whole  organism. 
This  working  together  results  in  — 

1 1 .  The  physiological  division  of  labor,  in  which  each  organ  works 
for  all  the  others,  and  is  dependent  on  all  the  other  organs. 

Questions. —  i.    What  are  some  of  the  ways  in  which  we  most  fre- 
quently violate  the  laws  of  health  ? 

2.  Name  the  more  important  organs  of  the  body  and  their  functions. 

3.  Name  the  different  tissues  of  one  of  these  organs. 


CHAPTER   II. 
MOTION. 

Motion  and  Life.  —  Motion  is  the  most  manifest  sign  of 
life.  While  we  are  sitting  still,  as  we  say,  there  are  fre- 
quent slight  motions  of  the  head,  body,  and  limbs.  Even 
during  sleep  the  movements  of  breathing  may  be  seen  ; 
the  hand  laid  upon  the  chest  may  feel  .the  beating  of  the 
heart,  and  the  finger  detect  the  pulse  in  a  number  of 
places. 

We  must  move  to  get  our  food,  or  at  least  to  eat  and 
digest  it.  Motion  is  necessary  for  breathing,  for  circu- 
lating the  blood,  for  getting  rid  of  wastes.  We  often  move 
to  avoid  injury. 

Motion  is  necessary  for  seeing :  we  must  turn  the  face 
toward  the  object;  we  move  the  eyeballs;  within  the  eye 
are  motions  to  regulate  the  amount  of  light  admitted,  and 
to  adapt  the  eye  for  seeing  at  different  distances. 

In  feeling,  we  put  forth  the  hand  to  touch  the  object. 
In  tasting,  we  touch  the  tongue  to  the  object.  In  smelling, 
we  sniff  ;  and  sniffing  is  a  respiratory  motion.  In  hearing 
and  in  speech  there  is  also  motion. 

How  are  all  these  motions  produced  ? 

Experiments  with  the  Muscles  in  our  own  Bodies.  —  i.  Clasp 
the  front  of  the  right  upper  arm ;  draw  up  the  forearm  strongly 
and  as  far  as  possible.  Note  what  changes  are  felt  in  the  biceps 
muscle. 

2.  Repeat  the  experiment,  and  with  the  thumb  and  finger  feel  the 
cord,  or  tendon,  at  the  lower  end  of  the  muscle,  just  within  the  angle  of 
the  elbow. 

7 


8  PHYSIOLOGY. 

3.  Place  a  weight  in  the  hand,  and  repeat  the  act,  noting  the  con- 
dition of  the  muscle  during  the  experiment ;  also  note  the  condition 
of  the  tendon. 

4.  Span  the  muscle,  placing  the  tips  of  the  fingers  in  the  angle  of 
the  elbow,  and  the  tip  of  the  thumb  as  far  as  you  can  up  the  arm ;  again 
bend  the  arm.     What  change  in  the  muscle  does  this  show  ?     Any 
muscle  that  bends  a  limb,  as  does  the  biceps,  is  called  a  flexor  muscle. 

5.  Clasp  the  back  of  the  right  upper  arm ;  forcibly  straighten  the 
arm.    The  muscle  lying  along  the  back  of  the  arm  is  the  triceps  muscle. 
It  is  called  an  extensor  muscle  because  it  extends,  or  straightens,  the 
arm. 

6.  Clasp  the   upper  side  of  the  right  forearm    near  the   elbow ; 
clench  the  right  hand  quickly  and  forcibly ;  repeat  rapidly. 

7.  Notice  the  thick  mass  of  muscle  at  the  base  of  the  thumb ; 
pinch  the  forefinger  and  thumb  strongly  together.     What  changes  can 
be  seen  and  felt  ? 

8.  Place  the  hand  on  the  outside  of  the  shoulder ;  raise  the  arm  to 
a  horizontal  position;  repeat  with  a  weight  in  the  hand. 


Fig.  2.    The  Shortening  and  Thickening  of  the  Biceps  Muscle  in  raising  the 
Forearm. 


9.  Stand  erect  with  the  heels  close  to  each  other,  but  not  quite 
touching;  let  the  arms  hang  freely  by  the  sides;  rise  on  tiptoes, 
without  moving  otherwise  ;  repeat  ten  times. 

10.  Place  the  tips  of  the  fingers  on  the  angles  of  the  lower  jaw; 
shut  the  teeth  firmly  on  a  piece  of  rubber,  and  note  the  bulging  of  the 
masseter  muscles. 


MOTION.  ,  9 

11.  Press  the  fingers  on  the  temples  ;  again  shut  the  jaw  firmly,  and 
feel  the  action  of  the  temporal  muscles. 

12.  Make  a  narrow  band  of  paper  that  will  snugly  fit  the  forearm 
when  the  hand  is  open ;  now  clench  the  fist  strongly. 

13.  With  a  tape  measure  take  the  circumference  of  the  upper  arm 
when  the  arm  hangs  free ;  again  when  the  forearm  is  strongly  flexed. 

14.  In  the  same  way  measure  the  forearm  when  the  hand  is  open, 
and  when  the  hand  is  clenched. 

By  these  experiments  we  learn  that  when  a  muscle  works  it  becomes 
shorter,  thicker,  and  harder. 

Nerves  and  Muscles  of  a  Rabbit's  Leg. —  In  the  hind  leg  of  a 
rabbit  the  sciatic  nerve  may  be  found  by  separating  two  large 
muscles  on  the  sides  of  the  thigh,  beginning  behind  the  knee  joint. 
The  shape  and  connections  of  the  muscles  may  be  learned,  and  also 
the  distribution  of  the  nerve. 

The  Action  of  Muscle.  —  The  action  of  muscle  is  always 
a  "pull."  The  muscle  shortens,  at  the  same  time  thick- 
ening and  hardening.  These  changes  in  muscle  are 
roughly  shown  in  the  preceding  experiments  of  feeling 
the  arm  during  its  action.  But  the  isolated  calf  muscle  of 
the  frog  may  be  made  to  prove  the  characteristic  changes 
with  great  clearness. 

Action  of  Frog's  Muscle.  —  A  frog  may  be  killed  painlessly  by  put- 
ting a  teaspoonful  of  ether  into  a  fruit  jar  of  water,  immersing  the  frog 
and  capping  the  jar.  When  the  frog  becomes  motionless,  its  head 
should  be  cut  off  and  a  wire  run  down  the  spinal  column  to  destroy  the 
spinal  cord.  After  cutting  the  skin  around  the  base  of  one  thigh  the 
skin  may  easily  be  stripped  from  the  whole  hind  limb.  If  the  muscles 
on  the  back  of  the  thigh  be  gently  separated  there  will  be  found  a  white 
thread  running  lengthwise,  the  sciatic  nerve.  It  should  be  severed 
near  the  hip  and  carefully  turned  down  upon  the  calf  muscle.  It  should 
not  be  pinched  or  dragged.  The  muscles  of  the  thigh  should  now  all 
be  cut  away,  being  careful  not  to  sever  the  nerve  near  the  knee.  The 
hip  joint  should  be  unjointed.  With  the  handle  of  the  scalpel  the  calf 
muscle  should  be  separated  from  the  shin  bone,  and  just  below  the 
knee  the  shin  bone  and  all  the  muscles  except  the  calf  muscle  severed 


10 


PHYSIOLOGY. 


It  now  the  heel  cord  be  cut  off  below  the  heel  there  will  remain  such  a 
preparation  as  is  represented  in  the  accompanying  figure,  consisting  of 
the  thigh  bone  with  the  calf  muscle  hanging  from  it,  and  the  sciatic 


—  Femur 

Origin       ~ 


Belly  of  Muscle   - 


Insertion 


Weight 


SHORTENED 


ELONGATED 


Fig.  3.    Action  of  the  Calf  Muscle  of  the  Frog,  showing  the  Relations  of  the 
Sciatic  Nerve. 


Origin 


Bundle  of  Muscle  Fibers 


nerve  still  connected  with  the  calf  muscle.     This  may  be  supported  by 
holding  the  end  of  the  thigh  bone  in  a  clamp  on  a  retort  stand.     A 

light  weight  should  be  attached  to 
the  heel  cord.  The  muscle  and 
nerve  should  be  moistened  with 
water  containing  a  little  salt.  On 
pinching  the  free  end  of  the  nerve, 
or  cutting  off  the  least  bit  with 
scissors,  the  muscle  will  be  made 
to  act.  The  shortening  and  thick- 
ening will  be  plainly  seen,  and 
by  taking  it  between  the  thumb 
and  finger  the  hardening  may  be 
felt. 


Muscle  Sheath 

CROSS   SECTION 


Tendon 


•Insertion 
LONGITUDINAL   SECTION 


Fig.  4.    The  Structure  of  Muscle. 


Structure    of    Muscle. — 

Chipped     beef     shows     well 
the  structure  of  muscle.    The 


MOTION. 


II 


white  network  is  the  connective  tissue.  In  the  meshes 
is  the  red  muscular  tissue.  The  partitions  which  run  all 
through  the  muscle  are  continuous  with  the  muscle  sheath, 
and  both  are  continuous  with  the  tendons  at  the  ends  of 
the  muscle.  In  fresh  muscle  the  sheath  and  the  parti- 
tions are  nearly  transparent,  and  are  not  easily  seen. 
When  the  meat  is  cooked  or  salted  the  connective  tissue 
becomes  white  and  opaque. 

Microscopic  Structure  of  Muscle.  —  In  frog's  or  rabbit's  muscle 
observe  the  thin,  transparent  membrane  covering  the  muscle,  the  muscle 
sheath.  With  forceps  tear  away  part  of  the 
muscle  sheath.  Tear  the  muscle  to  pieces, 
and  note  its  fibrous  structure.  A  shred  of 
muscle  may  be  mounted  in  a  drop  of  nor- 
mal saline  solution  on  a  slide,  and  exam- 
ined with  low  power  of  the  microscope.  If 
examined  with  a  higher  power  the  cross- 
markings,  or  striations,  will  be  seen.  Such 
muscle  is  called  striated  or  striped  muscle. 
All  of  the  muscles  used  in  ordinary  motions 
are  of  this  kind. 


Fig.  5.  Two  Muscular  Fibers 
showing  the  Terminations  of 
the  Nerves. 


Effects  of  Cooking  Muscle.  —  In 
well-cooked  corned  beef  the  connec- 
tive tissue  is  thoroughly  softened, 

and  the  muscle  fibers  are  easily  separated.  Thorough 
cooking,  especially  slow  boiling,  will  soften  the  connective 
tissue,  and  may  render  palatable  meat  that,  cooked  other- 
wise, would  be  exceedingly  tough  on  account  of  the  large 
amount  of  connective  tissue. 

Imitation  of  Structure  of  Muscle.  —  A  good  way  to 
represent  the  structure  of  muscle  is  to  take  a  number  of 
pieces  of  red  cord  to  represent  the  muscle  fibers.  Wrap 
each  in  white  tissue  paper ;  this  represents  the  individual 


12 

fiber  sheath.  Lay  a  number  of  these  side  by  side ;  wrap 
all  in  a  common  sheath ;  let  the  tissue  paper  project  be- 
yond the  threads,  and  here  compress  it  into  a  compact 
cylinder ;  this  last  corresponds  to  the  tendon. 

Connective  Tissue  the  Skeleton  of  Muscle.  —  If  all 
the  muscular  tissue  were  removed  from  a  muscle,  the 
sheaths  and  partitions  would  remain,  just  as  they  do  in  a 
squeezed  lemon  or  orange.  The  connective  tissue  forms 
a  framework  for  all  the  soft  tissues  of  the  body,  and  if 
their  working  cells  were  removed,  the  connective  tissue 
would  remain,  and  show  more  or  less  completely  the  form 
of  the  part.  Connective  tissue,  therefore,  may  be  called 
the  skeleton  of  the  soft  tissues.  Muscle  consists,  then, 
essentially  of  a  collection  of  soft,  transparent  tubes,  filled 
with  the  semi-fluid  muscle  substance.  By  scraping  the 
surface  of  a  steak  with  a  dull  knife  the  muscle  substance 
may  be  obtained,  leaving  the  connective  tissue.  This  is  a 
good  way  to  get  the  nutritious  part  of  beef  for  an  invalid. 

Importance  of  Muscles.  —  The  different  materials  of 
which  the  body  is  built  up  are  called  tissues.  Thus  we 
find  muscular  tissue,  bony  tissue,  nervous  tissue,  etc.  The 
muscles  make  up  nearly  half  of  the  weight  of  the  body. 
This  fact  of  itself  should  lead  us  to  consider  the  muscles 
of  high  importance.  Add  to  this  the  facts  above  noted, 
that  the  muscles  are  so  largely  concerned  in  the  nutrition 
of  the  body,  the  chief  agents  for  its  protection,  essential 
for  the  reception  of  ideas,  and  absolutely  indispensable  for 
the  expression  of  ideas,  and  we  can  see  the  reason  for 
beginning  the  study  of  physiology  with  the  examination 
of  the  muscles  and  their  action. 

Laws  of  Muscle  Action.  —  The  chief  characteristic  of 
muscle  is  its  ability  to  shorten ;  incidentally,  it  at  the 


MOTION'.  1 3 

same  time  thickens  and  hardens.  But  it  does  its  work  by 
shortening,  pulling  on  the  bones  by  means  of  the  strong, 
inelastic  tendons,  thus  producing  motion.  The  action  of 
the  muscle  as  a  whole  is  the  result  of  the  characteristics 
of  the  cells  of  which  it  is  composed.  The  individual  cells 
and  fibers  shorten,  and  their  combined  action  is  seen  in 
the  muscular  movement. 

Extent  of  Muscle  Shortening.  —  A  muscle  may  be 
made  to  shorten  one  third  of  its  length,  but  probably 
never  shortens  that  much  in  the  living  body. 

Duration  of  Muscle  Shortening.  —  A  muscle  cannot  be 
kept  shortened  for  any  great  length  of  time.  If  one  holds 
his  arm  out  horizontally  as  long  as  possible  he  soon  feels  ' 
fatigue,  later  pain,  and  he  may  feel  soreness  in  the  muscle 
for  several  days.  The  law  of  muscle  action  is  to  alternate 
periods  of  rest  with  periods  of  action.  In  many  exercises, 
as  in  walking,  the  limbs  act  alternately,  one  resting  or 
recovering  position  while  the  other  works. 

Alternate  Action  of  Flexors  and  Extensors.  —  If  we 

consider  the  biceps  and  triceps  of  the  arm,  we  see  that 
they  are  compelled  to  act  alternately  if  they  would  do 
effective  work.  They  might  both  shorten  at  the  same 
time,  and  are  made  to  do  so  in  such  an  attempt  as  that 
of  holding  the  arm  rigidly  bent  at  a  right  angle ;  as,  for 
instance,  in  wrestling  "  square  hold,"  in  which  case  one 
wishes  to  prevent  his  opponent  from  either  pushing  or 
pulling  him.  But  while  the  two  muscles  act,  no  motion  is 
produced.  When  the  flexor  shortens,  the  extensor  length- 
ens, and  vice  versa. 

Normal  Condition  of  Muscle.  —  The  muscles  are  always 
slightly  stretched,  as  shown  by  the  fact  that  when  a  cut 
is  made  into  a  muscle  the  wound  gapes  open ;  the  tension 


14  PHYSIOLOGY. 

of  the  muscle  is  further  shown  by  the  fact  that  when  a 
bone  is  broken,  as  in  the  upper  arm  or  thigh,  the  ends 
of  the  bones  slip  by  each  other,  and  the  limb  has  to  be 
strongly  stretched  to  bring  the  ends  back  together.  Mus- 
cles act  better  when  slightly  stretched,  and  probably  need 
a  slight  resistant  action  of  the  opponent  muscle. 

Symmetrical  Development  of  the  Muscles;  —  The  mus- 
cles of  the  two  sides  of  the  body  are  the  same  in  number 
and  arrangement.  At  birth  they  are  probably  about  equal 
in  size,  weight,  and  strength.  Most  persons  early  become 
right-handed,  and  the  greater  use  of  the  right  hand  and 
shoulder  makes  the  muscles  of  this  side  larger  and  heavier. 
The  muscles  pulling  on  the  bones  slightly  modify  them 
in  shape.  The  whole  body  may  become  noticeably  un- 
symmetrical.  Most  persons  step  harder  on  one  foot  than 
the  other,  as  shown  by  the  sound  of  the  footstep,  and  as 
shown  by  the  constant  wearing  of  one  shoe  sole  or  heel 
faster  than  the  other.  In  many  persons  one  shoulder  is 
habitually  carried  higher  than  the  other.  Symmetrical 
development  should  be  carefully  sought,  and  any  tendency 
to  a  one-sided  development  should,  so  far  as  possible,  be 
avoided.  We  should  use  the  left  hand  more.  There  are 
many  advantages  in  being  able  to  use  either  hand.  In 
carving,  in  shaving,  in  bandaging,  in  administering  medicine, 
it  may  be  necessary  to  use  the  left  hand  skillfully.  The 
pianist  and  the  harpist  use  the  two  hands  about  equally, 
while  the  violinist  puts  much  more  skill  into  his  left  hand. 
Trainers  of  athletes  often  begin  by  developing  the  left 
side  of  the  body  till  it  equals  the  right  in  size  and  strength. 

Muscles  the  Source  of  Strength.  —  Our  strength  de- 
pends on  our  muscles.  It  is  a  fine  thing  to  have  strong, 
well-developed  muscles,  not  only  because  they  give  beauty 


MOTION,  1 5 

of  form,  but  because  extra  strength  and  endurance  may 
be  needed  in  case  of  accident,  to  save  one's  own  life  or  that 
of  others.  In  a  case  of  fire  the  ability  to  climb,  to  go  up 
or  down  a  rope  "hand  over  hand,"  may  be  all  important. 
Any  one's  life  may  depend  on  his  ability  to  run  far  and 
swiftly,  to  swim,  to  jump,  or  to  lift  a  heavy  weight. 

Skeletal  Muscles.  —  When  we  look  at  the  skinned  car- 
cass of  an  animal  in  the  market,  we  observe  that  the  mus- 
cles almost  completely  cover  the  bones.  Those  which  are 
attached  to  the  bones  are  called  skeletal  muscles.  They  act 
upon  them  as  levers,  giving  to  motion  strength,  quickness, 
and  precision.  Without  bones  our  motions  would  be  like 
those  of  an  earthworm  or  slug,  slow  and  uncertain.  The 
muscles,  acting  through  the  bones,  can  lift  a  weight  that 
would  crush  the  muscles  if  laid  directly  upon  them,  while 
a  bone,  able  to  support  a  heavy  weight  without  being 
crushed,  has  no  power  in  itself.  The  muscles  have  active 
strength,  the  bones  have  passive  strength. 

Relation  of  the  Muscles  and  the  Bones.  —  Suspend  the  skeleton 
from  the  ceiling  in  the  most  open  space  in  the  room.  Let  the  pupils 
study  it ;  not  to  learn  the  names  of  all  the  bones,  but  to  get  a  general 
idea  of  the  forms  and  relations  of  the  parts.  It  is  well  to  have  the 
skeleton  constantly  at  hand,  to  show  the  location  of  the  various  organs 
as  they  are  taken  up.  If  possible,  supply  the  class  with  separate  bones 
from  another  skeleton,  and  let  the  pupils  place  each  separate  bone 
alongside  the  corresponding  one  in  the  complete  skeleton. 

Pass  to  the  skeleton,  and  locate  the  biceps  muscle.  After  examining 
Fig.  2,  show  the  points  of  its  origin  and  insertion.  Feel  the  biceps 
of  your  arm.  Note  that  its  thickest  part  is  opposite  the  most  slender 
part  of  the  bone.  But  at  the  enlarged  end  of  the  bone  the  muscle  has 
narrowed  to  a  slender  tendon,  which  passes  over  the  joint  to  be  attached 
to  the  next  bone,  thus  giving  more  slenderness,  flexibility,  and  freedom 
of  motion  to  the  joint.  The  muscle  which  closes  the  mouth,  as  in 
pursing  up  the  lips,  is  not  attached  to  any  bone,  but  in  shortening 
reduces  the  aperture. 


1 6  /'//}'S/OUhi}'. 

Flexion  of  the  Forearm.  —  Take  the  bones  of  the  arm  that  are 
articulated  (if  there  is  not  an  artificial  hinge  at  the  elbow,  one  can 
readily  be  made  of  wire)  ;  put  a  strong  rubber  band  in  place  of  the 
biceps  muscle ;  fasten  this  to  the  head  of  the  humerus  by  cords,  and 
by  the  lower  end  to  the  radius,  where  the  rough  place,  an  inch  or  so 
from  the  elbow  joint,  shows  the  insertion  of  the  tendon.  Have  the 
rubber  stretched  so  that  when  not  held  it  will  flex  the  forearm.  This 
will  serve  to  show  the  action  of  the  biceps,  though  we  must  be  careful 
to  bear  in  mind  that  the  muscle  does  not  pull  the  arm  up  because  it  has 
been  stretched,  as  is  the  case  with  the  rubber.  In  the  case  of  the 
muscle,  we  know  that  the  live  muscle  has  the  power  of  shortening  when 
stimulated,  and  in  this  respect  is  totally  unlike  the  rubber.  The  live 
cells,  or  units,  act  in  concert. 

Levers.  —  The  essentials  of  a  lever  are  the  point  about 
which  the  lever  turns,  called  the  fulcrum,  the  place  where 
the  power  is  applied,  called  the  power,  and  the  part  to  be 
moved,  called  the  weight.  In  the  body,  the  fulcrum  is 
some  joint,  the  power  is  the  place  where  the  muscle  is 
attached,  and  the  weight  is  the  part  to  be  moved. 

Kinds  of  Levers.  —  In  flexing  the  forearm,  the  weight 
is  the  hand  or  the  hand  and  what  is  in  it ;  the  fulcrum  is 
the  elbow  joint ;  and  the  power  is  the  point  where  the 
tendon  of  the  biceps  is  attached  to  the  radius.  This  kind 
of  a  lever  is  what  the  books  call  a  lever  of  the  third  class. 
The  triceps,  on  the  back  of  the  arm,  pulls  on  the  projection 
of  the  ulna  (the  inner  bone  of  the  forearm  when  the  palm 
is  up),  back  of  the  elbow.  The  elbow  is  here,  also,  the 
fulcrum,  and  the  hand  (or  the  object  to  be  pushed  by  the 
hand)  is  the  weight.  This  kind  of  lever,  where  the  fulcrum 
is  between  the  power  and  the  weight,  is  called  a  lever  of  the 
first  class.  In  raising  the  weight  of  the  body,  by  stand- 
ing on  tiptoe,  we  use  a  lever  of  the  second  class.  Here 
the  ball  of  the  foot  is  the  fulcrum.  The  weight  is  the 
weight  of  the  whole  body,  resting  on  the  ankle  joint,  while 


MOTION.  I/ 

the  power  is  the  calf  muscle.     We  may  find  many  exam- 
ples of  levers  in  the  body  if  we  look  for  them. 


(1)  Tapping  on  Floor.  (2)  Rising  on  Toe.  (3)  Lifting  Weight. 

Fig.  6.    Three  Kinds  of  Levers  as  shown  by  the  Foot. 

P  —  Power.     W  —  Weight.     F  —  Fulcrum. 

Kinds  of  Levers  shown  by  the  Foot.  —  The  different 
classes  of  levers  may  be  further  illustrated  by  different 
motions  of  the  foot.  In  tapping  the  toes  on  the  floor 
while  the  heel  is  lifted,  or  in  pressing  down  the  ball  of  the 
foot  while  running  the  treadle  of  a  sewing  machine,  we 
have  an  example  of  a  first-class  lever.  In  raising  the 
weight  of  the  body  on  tiptoes,  or  as  the  foot  is  used  in 
taking  each  step,  the  foot  is  used  as  a  lever  of  the  second 
class.  When  one  lifts  a  weight  with  the  toes,  the  foot  is 
used  as  a  lever  of  the  third  class.  These  three  classes  of 
levers  are  illustrated  in  the  accompanying  figures. 

Advantages  and  Disadvantages  of  Levers  in  the  Body.  —  The 

action  of  the  bones  of  the  forearm  as  a  lever  may  perhaps  be  better 
understood  by  the  following  considerations :  If  the  arm  consisted 
merely  of  the  biceps,  suspended  from  the  shoulder,  it  is  evident  that 
its  only  action  would  be  a  straight  pull.  Suppose  the  biceps,  thus 
hanging  alone  from  the  shoulder,  had  a  hook  at  its  lower  end,  it  could, 
when  it  shortened,  lift  a  weight  just  as  far  as  it  shortened,  and  no 


i8 


PHYSIOLOGY. 


farther.  It  could  not  swing  the  wi:ight  outward,  or  push  it  upward. 
But  from  the  way  in  which  the  biceps  is  attached  to  the  forearm,  when 
the  muscle  shortens  an  inch  it  may  move  the  hand  a  foot.  Of  course 
the  hand  moves  much  faster,  and  we  have  a  great  gain  in  speed  by 
reason  of  this  lever  arrangement.  But  we  cannot  lift  so  heavy  a  weight 

at  this  faster  rate,  as  we  could  at  the 
elbow.  For  instance,  suppose  one  were 
to  carry  a  heavy  basket  with  a  bail 
handle  by  slipping  the  arm  through 
the  bail  up  to  the  elbow.  Now.  it  is 
evident  that  the  biceps  is  supporting 
the  weight.  If  it  is  as  heavy  as  can  be 
held  here,  we  know  that  we  could  not 
hold  the  same  weight  in  the  hand  with 
the  elbow  bent  at  a  right  angle. 


Ball 


Articular  Extremity 


Medullary  Cavity 


—  Hard  Bone 


Study  of  One  of  the  Long  Bones. 
—  For  this,  take,  preferably,  a  femur 
or  a  humerus.  Let  us  suppose  we  ha\  »• 
a  femur. 

1.  Observe  its  shape,  —  cylindrical, 
somewhat  curved,  enlarged  at  the  ends. 

2.  The   ends  have  smooth  places, 
where  they  fitted  other  bones. 

3.  Along  the  sides,  especially  near 
the  ends,  are  ridges  and   projections, 
where  the  muscles  were  attached. 

4.  There  are    small    holes    in    the 
bone,  where  blood  tubes  passed  in  and 
out. 

5.  Saw  a  femur  in  two,  lengthwise, 
and  make  a  drawing  showing :  — 

(#)    The  central  marrow  cavity. 

(£)  The  spongy  extremities,  noting  especially  the  directions  of  the 
bony  plates  and  fibers. 

6.  Observe  the  width  of  the  lower  end  of  the  femur,  where  it  rests 
on  the  tibia.  Suppose  these  two  bones  were  as  narrow  at  their  ends, 
where  they  meet  to  form  the  knee  joint,  as  they  are  at  their  centers, 
what  kind  of  a  joint  would  they  make  ?  Illustrate  by  piling  up  a  num- 


Spongy  Bone 

Articular  Extremity 

r.  7.     Longitudinal  Section  of 
Femur. 


MOTION. 


her  of  spools  on  end ;  the  column  is  more  lightened  than  it  is  weak- 
ened by  the  hollowing  out  of  the  sides  of  each  spool.  And  the  central 
hollow  of  the  spool  does  not  greatly  weaken  it.  A  given  weight  of 
material  has  more  strength  when  in  the  form  of  a  hollow  cylinder.  The 
bones  combine  well  two  very  desirable  quali- 
ties, lightness  and  strength.  If  in  our  col- 
umn of  spools  we  place  a  wide  rubber  band 
around  the  junction  of  two  spools,  we  have 
something  very  similar  to  the  capsular  liga- 
ment, which  surrounds  the  joints. 

Joints.  —  The  ends  of  the  bones,  where 
they  fit  together  in  the  joints,  are  covered 
with  a  layer  of  smooth,  elastic,  whitish  or 
transparent  cartilage.  The  motion  in  the 
joints  is  made  still  more  easy  by  the  synovia, 
resembling  white  of  egg.  The  ends  of  the 
bones  are  held  together  by  tough  bands  and 
cords  of  ligament,  a  form  of  connective 
tissue  very  much  like  tendon.  Bones  are 
closely  covered  by  a  tough  coat  of  connective 
tissue  called  the  periosteum. 

All  these  structures  can  easily  be  found 
by  dissecting  a  sheep  shank  gotten  from  the 
butcher,  or  in  the  hind  leg  of  a  rabbit. 

Locomotion.  —  Locomotion  is  mov- 
ing from  place  to  place  and  should 
be  distinguished  from  mere  motion. 
By  continuing  such  observations  as 
we  made  when  we  began  to  study 
our  motions,  we  can  analyze  and 
understand  many  of  the  common 
movements  which  we  habitually 
make. 

Standing.  —  Although  we  are  not  ordinarily  conscious  of 
the  fact,  when  we  are  standing  still  we  are  using  many 
muscles.  The  accompanying  figure  illustrates  how  some 


Action  of  the  Muscles 
in  Standing. 


20  PHYSIOLOGY. 

of  the  muscles  act  in  keeping  the  body  upright.  Our 
weight,  or,  we  would  better  say,  the  force  of  gravity,  is 
continually  trying  to  pull  us  down  to  the  ground.  The 
joints  are  all  freely  movable,  and  hence  as  soon  as  the 
muscles  cease  to  act  properly,  in  balancing  against  each 
other,  we  lose  our  equilibrium,  and  fall  if  we  do  not 
quickly  regain  it. 

Walking.  —  In  walking,  we  lean  forward,  and  if  we  take 
no  further  action  we  fall.  But  we  keep  one  foot  on  the 
ground,  pushing  the  body  forward,  while  the  other  leg  is 
flexed  and  carried  forward  to  save  us  from  the  fall.  We 
catch  the  body  on  this  foot,  and  repeat  the  action.  To 
show  how  we  are  really  repeatedly  falling  and  catching 
ourselves,  recall  how  likely  one  is  to  fall  if  some  obstacle 
is  placed  in  the  way  of  the  foot  as  it  moves  forward  to 
catch  the  weight  of  the  body. 

Running.  —  In  running,  the  action  is  more  vigorous. 
The  propulsion  by  the  rear  leg  is  now  greater.  It  gives 
such  a  push  as  to  make  the  body  clear  the  ground,  whereas 
in  walking,  the  rear  foot  is  not  lifted  till  the  front  foot 
touches  the  ground.  But  in  running  there  is  a  time  when 
both  feet  are  off  the  ground. 

Locomotion  by  Reaction.  — Take  two  broomsticks  and  place  them 
crosswise  under  the  ends  of  a  board.  Run  along  the  board.  This 
shows  that  the  direct  effort  in  running  is  to  push  one's  support  from 
under  him.  When  a  horse  plunges  forward  in  the  mud,  he  only  thrusts 
his  feet  farther  into  the  mud.  Our  effort  in  progression  is  primarily  to 
push  the  earth  out  from  under  us,  and  it  is  by  reaction  that  we  go 
forward.  It  is  the  same  problem  with  the  fish  swimming  forward  by 
striking  backward  and  sideways  against  the  water,  and  with  the  bird 
beating  downward  and  backward  upon  the  air. 

Bones  combine  Lightness  and  Strength. — The  mus- 
cles, then,  make  use  of  the  bones  as  levers.  We  carry 


MOTION.  21 

these  levers  with  us  all  the  time.  Hence  the  desirability 
of  having  them  as  light  as  is  consistent  with  the  requisite 
degree  of  strength.  The  body  follows  the  same  law  of 
mechanics  that  we  use  outside  of  the  body.  A  hollow 
pillar  or  hollow  tube  has  a  greater  strength  than  the  same 
amount  of  material  in  the  form  of  a  solid  cylinder.  The 
long  bones  of  the  limbs  are  hollow,  and  near  their  ends, 
where  we  have  found  that  they  need  to  be  enlarged,  we 
find  a  spongy  structure,  where  lightness  and  strength  are 
secured  by  the  interlacing  fibers  and  plates  of  bony 
material. 

Uses  of  Bones.  —  The  part  that  the  bones  play  is  of  a 
passive  nature ;  they  support  the  tissues,  protect  some 
parts,  and  serve  as  levers  on  which  the  muscles  act.  We 
may  not  call  the  bones  dead  tissues,  for  they  receive  blood 
and  grow.  But  the  active  muscles  use  them  as  a  man  uses 
a  crowbar,  as  a  mere  tool.  It  will  therefore  be  more 
interesting  to  return  to  the  muscles,  and  learn  the  causes 
and  conditions  of  their  activity. 

What  makes  Complex  Muscular  Action  Harmoni- 
ous.—  Have  you  ever  seen  two  persons,  each  using  the 
right  hand,  try  to  sew,  one  holding  the  cloth,  the  other 
using  the  needle  ?  Would  they  get  along  well  ?  Suppose 
one  were  to  hold  the  needle,  and  the  other  were  to  try  to 
thread  it,  each  using  one  hand  ?  Why  is  it  that  the  right 
hands  of  two  persons  cannot  work  so  well  together  as  the 
right  and  left  hands  of  one  person  ?  What  connection  is 
there  between  the  two,  that  one  knows  just  what  the  other 
is  doing  and  when  it  does  it  ?  Why  can  two  individuals 
never,  with  any  amount  of  practice,  work  so  in  unity  as  the 
parts  of  the  individual  ? 


22  PHYSIOLOGY. 

Let  us  seek  the  answers  to  these  questions  in  the  follow- 
ing lessons. 

READING.  —  How  to  Get  Strong  and  How  to  Stay  So^ 
Blaikie  ;  Sound  Bodies  for  Onr  Boys  and  Girls,  Blaikie ; 
Physiology  of  Bodily  Exercise,  Lagrange. 

Summary.  —  i .  Motion  is  involved  in  nearly  every  activity  of  the 
body. 

2.  The  action  of  muscle  is  a  shortening,  accompanied  by  a  thick- 
ening and  hardening. 

3.  Muscle  consists  of  fibers  with  a  connective  tissue  sheath  for 
each  fiber,  bundle  of  fibers,  and  for  the  muscle  as  a  whole. 

4.  The  skeletal  muscle  fibers  are  striated. 

5.  The  muscles  make  about  half  the  body's  weight. 

6.  Muscles  may  shorten  one  third  their  length. 

7.  They  cannot  remain  shortened  long  at  a  time. 

8.  The  muscles  should  be  developed  symmetrically. 

9.  In  the  limbs  the  muscles  are  fusiform  and  have  their  greatest 
diameter  opposite  the  central,  or  narrower,  portions  of  the  bones,  con- 
cealing the  fact  that  the  bones  are  largest  at  the  ends,  as  is  so  manifest 
in  the  skeleton. 

10.  The  bones  serve  as  levers  by  which  the  muscles  exert  their 
force. 

1 1 .  The  bones  of  the  limbs  are  hollow  cylinders  combining  lightness 
-and  strength. 

12.  The  joints  have  a  smooth  motion   due  to   the   cartilage   and 
synovia. 

13.  Locomotion  is  brought  about  by  reaction. 

Questions.  —  i .  What  effect  is  produced  by  carrying  a  heavy  satchel 
for  a  long  distance  without  resting? 

2.  Which  is  more  tiresome,  standing  still  or  walking?     Why? 

3.  When  the  boy,  who  thinks  he  can  strike  a  hard  blow,  says, 
••  Feel  my  muscle,'1  does  he  usually  call  attention  to  the  muscle  used  in 
striking? 

4.  Find  other  examples  of  levers  in  the  body. 

5.  Find  examples  of  the  three  kinds  of  levers,  not  in  the  body, 
which  we  use  often. 


MOTION.  23 

6.  Why  is  it  easier  to  sit  with  one  leg  crossed  over  the  other? 

7.  What  is  the  effect  on  muscles  of  light  clothing? 

8.  How  may  the  arms  be  used  to  illustrate  the  three  kinds  of 
levers  ? 

9.  Analyze  and  explain  jumping,  hopping,  etc. 

10.  What   is   "curvature  of  the  spine"?      How  caused  and  how 
avoided  ? 

1 1 .  What  makes  people  bow-legged  ? 

12.  Why  are  the  sides  of  the  body  often  sore  after  walking  on  icy 
pavements  ? 


CHAPTER    III. 

THE   GENERAL  FUNCTIONS    OF    THE   NERVOUS  SYSTEM. 
—  SENSATION  AND  MOTION. 

What  makes  Muscles  Shorten  ?  —  We  have  seen  that 
the  muscles  have  the  power  of  shortening ;  that  in  shorten- 
ing they  act  on  the  bones  as  levers  to  produce  our  varied 
motions.  What  makes  the  muscles  shorten  ? 

Voluntary  and  Involuntary  Motions.  —  Some  motions 
we  will  to  make.  We  will  to  sit,  to  stand,  to  walk,  to  run, 
or  to  stretch  out  the  hand.  Such  motions,  originating  in 
a  brain  activity,  are  called  Voluntary.  Other  motions  are 
Involuntary.  The  will  does  not  control  the  heart  beat. 
Most  persons  cannot  keep  from  winking  when  a  quick 
motion  is  made  toward  the  face,  even  if  they  know  they 
will  not  be  hit.  But  all  of  these  motions,  whether  volun- 
tary or  involuntary,  are  dependent  upon  the  nervous 
system. 

The  Cerebro-spinal  Nervous  System.  —  This  consists 
of  the  brain,  the  spinal  cord,  and  the  spinal  nerves.  The 
brain  will  be  described  later. 

The  Spinal  Cord.  —  The  spinal  cord  is  a  cylindrical 
body  extending  from  the  brain  along  the  cavity  of  the 
spinal  column.  Its  diameter  is  not  uniform  throughout. 
Between  the  shoulders  is  an  enlargement  called  the  cer- 
vical enlargement,  where  the  large  nerves  are  given  off  to 

24 


NERVOUS  SYSTEM. 


Fig.  9.    Diagram  showing  Arrangement  of  Nervous  System. 


26  PHYSIOLOGY. 

the  arms.  In  the  region  of  the  loins  is  the  lumbar  enlarge- 
ment, where  the  nerves  are  given  off  to  supply  the  poste- 
rior limbs.  The  cord  is  not  so  long  as  the  cavity  of  the 
spinal  column,  and  the  space  posterior  to  the  cord  is  occu- 
pied by  the  nerves  extending  to  the  posterior  limbs,  and 
these  nerves  are  given  off  at  a  very  sharp  angle,  and  con- 
tinue backward  for  some  distance  before  they  emerge 
from  the  cavity  of  the  spinal  column.  But  in  the  region 
of  the  shoulders  the  nerves  spring  off  at  about  a  right 
angle  with  the  cord.  The  outside  of  the  cord  is  white,  but 
the  central  portion  consists  of  what  is  called  gray  matter. 
The  white  portion  is  made  up  of  fibers,  but  the  gray  matter 
consists  of  nerve  cells  as  well. 

The  Spinal  Nerves.  — These  are  given  off  in  pairs  from 
the  sides  of  the  spinal  cord,  passing  out  between  the  suc- 
cessive vertebrae.  In  the  regions  of  the  shoulders  and 
loins  the  spinal  nerves  are  large,  as  they  supply  the  large 
muscles  of  the  limbs  ;  but  in  the  middle  of  the  back,  where 
only  the  muscles  of  the  body  wall  are  supplied,  the  nerves 
are  small.  We  have  thirty-one  pairs  of  spinal  nerves. 

The  Roots  of  the  Spinal  Nerves.  —  Each  spinal  nerve 
arises  by  two  roots,  one  nearer  the  back,  called  the  dorsal 
root,  the  other  nearer  the  ventral  surface,  the  ventral  root. 
These  two  roots  soon  unite  to  form  one  spinal  nerve. 

The  Ganglion  of  the  Dorsal  Root.  —  On  the  dorsal 
root,  just  before  it  unites  with  the  ventral  root,  is  a  swell- 
ing, the  ganglion  of  the  dorsal  root.  Like  all  ganglions,  it 
is  largely  made  up  of  nerve  cells,  being  a  center  of  con- 
trol rather  than  a  means  of  communication. 

The  Cerebro-spinal  Nervous  System  of  the  Rabbit  or  Cat. —  It 
will  prove  helpful  at  this  point  to  examine  the  nervous  system  of  a 


NERVOUS  SYSTEM.  2*] 

rabbit.  The  animal  may  be  killed  painlessly  by  shutting  it  in  a  tight 
box  with  a  sponge  holding  a  teaspoonful  of  chloroform  or  ether.  The 
smaller  the  box,  the  less  anesthetic  necessary.  A  large  glass  jar  inverted 
over  the  animal  is  convenient. 

For  a  support,  nail  a  foot  of  two-by-four  scantling  edgewise  to  a  base 
board.  Lay  the  animal  on  this  and  tack  out  the  feet.  Slit  and  pull 
aside  the  skin  from  the  nose  along  the  back  to  the  base  of  the  tail. 
Remove  the  muscle  along  the  sides  of  the  back  and  neck.  Between 
the  skull  and  the  first  vertebra  is  a  space  covered  by  a  thin  membrane. 
This  may  be  cut  through  with  scissors.  Then  bone  forceps  may  be 
employed  by  inserting  the  point  of  a  blade  on  each  side  of  the  cord  and 
cutting  through  the  bone.  In  this  way  the  whole  of  the  dorsal  portion 
of  the  spinal  column  may  be  removed,  exposing  the  spinal  cord  through- 
out its  entire  length.  With  care  the  nerves  and  their  roots  may  be 
found.  The  nerves  extending  to  the  anterior  limbs  are  easily  traced, 
but  for  the  nerves  to  the  posterior  limbs  more  work  is  needed. 

Structure  of  Nerves.  — When  we  trace  the  sciatic  nerve 
outward,  we  find  that  it  is  continually  subdividing.  This 
division  continues  until  the  branches  are  too  small  to  be 
seen  by  the  naked  eye.  Microscopic  examination  shows 
that  a  nerve  is  made  up  of  a  great  number  of  fibers  bound 
together  in  a  common  sheath  of  connective  tissue,  as  is 
the  case  with  muscle.  When  the  nerve  divides  there  is 
ordinarily  no  true  branching  or  forking,  but  certain  of 
the  fibers  simply  separate  from  the  rest,  as  in  the  separa- 
tion of  the  fibers  in  floss  silk. 

Structure  of  a  Nerve  Fiber.  —  A  single  nerve  fiber  is 
too  small  to  be  seen  by  the  naked  eye,  being  only  about 
one  two-thousandth  of  an  inch  in  diameter.  It  consists  of 
the  following  parts  :  — 

1.  The  Axis  Cylinder,  a  central  strand,  or  core,  of  semi- 
transparent,  gray  material. 

2.  The   Medullary    Sheath    is    a   layer    of    white,    oily 
material  around  the  axis  cylinder. 


28  rnvsjoLOGY. 

3.  The  Nerve  Fiber  Sheath  is  a  thin,  transparent  outer 
sheath  of  cdnnective  tissue. 

Function  of  Nerve  Fibers.  -The  sole  function  of  the 
nerve  fiber  is  to  convey  nerve  impulses.  The  nerve  im- 
pulse passes  along  the  axis  cylinder  as  an  electric  current 
passes  along  an  insulated  wire. 

Nerve  Fiber  Sheath 


Axis  Cylinder 


Medullary  Sheath 
Fig.  1 0.    Structure  of  a  Nerve  Fiber. 

Gray  Nerve  Fibers.  —  In  the  sympathetic  nerves  there 
are  many  fibers  which  have  no  medullary  sheath,  but  con- 
sist simply  of  the  axis  cylinder  and  the  nerve-fiber  sheath. 
These  are  called  gray  nerve  fibers. 

Cross-section  of  the  Spinal  Cord.  —  If  a  thin  slice  of 
the  spinal  cord  be  made  as  shown  in  Fig.  11,  it  will  be 
seen  that  the  central  part  is  darker  in  color  than  the  outer 
part.  The  central  part  is  known  as  the  gray  matter,  in 
distinction  from  the  rest,  which  is  called  the  white  matter. 
The  white  matter  of  the  nervous  system  is  made  up  of 
nerve  fibers  whose  structure  and  use  we  have  just  con- 
sidered. But  the  gray  matter  has  a  different  structure  and 
a  different  function.  Instead  of  being  made  up  mainly  of 
fibers  it  is  composed  of  cells,  one  of  the  forms  of  which  is 
represented  in  Fig.  12.  Some  of  the  branches  of  these 
cells  are  continued,  and  become  the  axis  cylinders  of  nerves, 
and  it  is  believed  that  every  nerve  fiber  begins  as  a  branch 
of  some  nerve  cell.  One  of  the  best  places  to  see  these 
nerve  cells  is  in  the  gray  matter  of  the  spinal  cord,  near 


NERVOUS  SYSTEM.  29 

the  place  where  the  ventral  root  of  the  spinal  nerve  arises. 
This  part  of  the  gray  matter  is  called  the  ventral  horn  of 
the  gray  matter.  If  this  portion  be  examined  under  a 
moderately  high  power  of  the  microscope,  there  may  be 
seen  a  number  of  cells  with  radiating  branches. 


Dorsal  or  Sensor 
Root 


Ganglion 

i 

Ventral  or  Motor  Root 

Fig.  1 1 .    Cross-section  of  Spinal  Cord. 

Functions  of  the  Spinal  Cord. — The  spinal  cord  has 
two  main  functions  :  — 

1.  Its  conducting  power,  by  means  of  the  white  fibers 
which  make  up  the  outer  part  of  the  cord.     These  fibers 
may  be  regarded  as  connecting  the  gray  matter  of  the 
brain  with  all  parts  of  the  body. 

2.  The  gray  matter  is  the  center  of  the  reflex  actions  of 
the  cord. 

Ganglia.  —  Masses  of  nerve  cells  make  up  nerve  centers, 
or  ganglia,  such  as  are  on  the  dorsal  roots  of  the  spinal 
nerves.  These  also  would  show  under  the  microscope 
that  their  chief  constituent  is  a  collection  of  nerve  cells 
which  give  off  one  or  more  branches. 


30  /V/KVA  >/.(;<;r. 

The  gray  matter  of  the  spinal  cord  is  considered  LI  col- 
lection of  ganglions.  We  see  that  the  outer  layer  of  the 
brain  is  grayish  in  color.  Within  is  white  matter,  consist- 
ing of  nerve  fibers  that  connect  the  cells  of  the  gray  layer 


Fig.  12.    A  Large  Nerve  Cell  from  the  Gray  Matter  of  the  Spinal  Cord. 

with  the  various  parts  of  the  body  through  the  base  of  the 
brain,  the  spinal  cord,  and  spinal  nerves. 

No  Sensation  without  the  Brain.  —  After  a  fowl's  head  is  cut  off  it 
"  flops  "  around  for  some  time,  and  it  may  even  jump  clear  from  the 
ground.  If  one  takes  hold  of  its  feet  to  pick  it  up,  it  may  begin  to 
struggle  as  if  it  were  trying  to  escape. 

Now,  we  know  that  the  bird  cannot  feel  anything  after  its  head  is 
cut  off,  because  the  body  is  completely  separated  from  the  brain,  which 
is  the  center  of  sensation.  So  with  the  frog.  After  its  head  is  cut 
off,  it  cannot  feel  anything. 

Reflex  Action  of  the  Spinal  Cord  of  the  Frog.  —  A  frog  may  be 
killed  as  directed  on  p.  9.  Cut  off  its  head  and  suspend  the  body 
from  any  convenient  support,  such  as  the  ring  of  a  retort  stand. 

1.  On  pinching  the  toes  the  foot  will  be  drawn  up. 

2.  The  sciatic  nerve  should    now  be  severed   as   before   directed 
(p.  9).      At  the  instant  of  cutting  the  nerve  the  muscles  below  will 
twitch,  because  the  nerve  fibers  running  to  them  are  stimulated. 


NERVOUS  SYSTEM.  31 

3.  If  the  toes  are  again  pinched,  it  is  found  that  the  uninjured  leg 
will  draw  up,  but  not  the  one  whose  sciatic  nerve  has  been  severed. 

4.  If  a  wire  be  run  down  the  spinal  cavity,  the  spinal  cord  will-  be 
destroyed,  and  during  the  operation  the  uninjured  leg  will  act  spas- 
modically, because  the  nerve  fibers  going  to  its  muscles  from  the  cord 
are  stimulated. 

5.  Pinching  the  toes  no  longer  gives  response,  because  the  cord, 
which  acted  as  the  center  of  this  reflex  action,  is  destroyed. 

The  Gray  Matter  of  the  Cord  the  Center  of  Reflex 
Action.  —  In  simple  sensation  of  touch,  pressure  on  the 

Afferent  Dorsal  Root 

Sensor  Fiber 


Skin 


Motor  Fiber  vv 

Efferent  Ventrg|  Root 

Fig.  1 3.     Diagram  of  Reflex  Action  of  the  Spinal  Cord. 
(After  Landois  and  Stirling.) 

toes  starts  a  nerve  current  or  nerve  impulse  which  runs  up 
to  the  brain.  The  sensation  is  in  the  brain,  but  is  referred 
to  the  foot.  Hence  we  should  be  careful  not  to  speak  of 
a  sensation  being  carried.  In  voluntary  muscular  action 
the  impulse  starts  from  the  brain,  goes  to  the  muscles,  and 
makes  them  shorten  or  relax. 

But  in  reflex  action  the  current  runs  up  the  nerve  to  the 
spinal  cord.  The  gray  matter  of  the  central  part  of  the 
cord  receives  the  message,  and  sends  back  a  nerve  impulse 
to  the  muscles  to  make  them  shorten  and  pull  the  foot 
away  from  the  source  of  injury. 


32  PHYSIOLOGY. 

The  Parts  Essential  to  Reflex  Action  of  the  Spinal 
Cord :  - 

1.  A  sensitive  surface  (the  skin,  for  instance). 

2.  Afferent  nerve  fibers. 

3.  A  nerve  cell,  or  cells,  in  the  center  of  the  spinal  cord. 

4.  Efferent  nerve  fibers. 

5.  Working  organ,  as  muscle  or  gland. 

Phases  of  Reflex  Action.  —  In  the  above  experiment 
on  the  frog  the  steps  in  order  were  :  — 

1.  Stimulation  of  the  nerve  endings  in  the  skin  of  the 
toe. 

2.  Passage  of  a  nerve  impulse  up  the  afferent  fibers  to 
the  spinal  cord. 


Nerve-Cell 


Afferent  Fiber ^  \        ,_„  _., 

x  —  Efferent  Fiber 


Skin  — !, 

&--  Muscle 

Fig.  14.    Scheme  of  Reflex  Arc. 

3.  Reception  of  the  impulse  by  a  cell,  or  cells,  of  the 
gray  matter  in  the  cord. 

4.  Sending  back  a  nerve  impulse 

5.  Along  an  efferent  fiber,  or  fibers,  to 

6.  Muscles  which  shorten  and  move  the  foot. 

Importance  of  Reflex  Action.  —  It  is  important  that 
we  understand  the  nature  of  reflex  action,  for  very  many 
of  the  processes  of  the  body  are  regulated  by  it.  Not 
only  the  more  manifest  motions,  such  as  winking  when 


NERl/OUS  SYSTEM.  33 

anything  comes  quickly  toward  the  eye,  dodging,  jumping 
when  suddenly  touched  by  anything  hot  or  when  pricked 
by  a  pin,  but  also  the  adjustments  of  the  essential  processes 
of  life,  circulation,  respiration,  and  digestion,  are  brought 
about  through  reflex  action. 

Destination  of  Nerve  Fibers.  —  The  sciatic  nerve  is 
composed  of  many  fibers.  If  this  nerve  is  traced  outward, 
it  is  found  to  be  continually  subdividing,  and  sending  small 
branches  to  the  muscles,  and  finally  in  the  muscles  one 
fine  nerve  fiber  goes  to  each  muscle  fiber.  (See  Fig.  13.) 
Many  fibers  go  on  past  the  muscles  to  the  skin.  We  can 
feel  in  any  part  of  the  skin,  and  we  can  tell  just  where  we 
are  touched.  These  fibers  from  the  skin,  then,  carry 
nerve  impulses  inward,  as  those  going  to  the  muscles 
carry  impulses  outward. 

Nerve  Roots  and  their  Functions.  —  Experiments  on 
the  lower  animals,  and  accidents  in  the  case  of  man,  show 
that  all  the  fibers  of  the  nerves  that  carry  currents  to  the 
muscles  pass  out  from  the  spinal  cord  into  the  ventral 
root,  and  that  all  the  fibers  that  carry  currents  inward 
enter  the  spinal  cord  through  the  dorsal  root.  Hence,  the 
dorsal  root  is  often  called  the  afferent  root,  and  the  ventral 
the  efferent  root.  Since  ingoing  impulses  produce  sensa- 
tion, the  dorsal  root  is  called  the  sensory  root,  while  the 
ventral  root,  carrying  currents  outward  to  produce  motion, 
is  called  the  motor  root. 

Effect  of  Stimulating  a  Spinal  Nerve.  —  Experiments 
have  shown  that  if,  in  an  uninjured  animal,  a  nerve,  or 
more  properly  a  nerve  trunk,  —  as  the  sciatic  nerve,  —  be 
stimulated,  for  instance,  by  a  suitable  electric  shock,  two 
effects  are  produced :  first,  motion  in  the  parts  whose 


34  PHYSIOLOGY. 

muscles  are  supplied  by  the  nerve ;  second,  sensation, 
which  is  referred  to  the  parts  of  the  skin  supplied  by  the 
branches  of  the  nerve. 

Effect  of  Severing  a  Spinal  Nerve.  —  If.  instead  of  simply  stimu- 
lating the  nerve,  the  nerve  is  severed,  the  same  two  effects  will  he  pro- 
duced. After  severing  the  nerve,  if  we  stimulate  the  end  of  the  nerve 
still  connected  with  the  limb,  we  get  action  of  the  muscles  in  that  limb. 
If  we  stimulate  the  end  of  the  nerve  connected  with  the  body,  a  sensa- 
tion will  be  produced,  and  this  sensation  will  be  referred  to  the  parts 
from  which  the  nerve  fibers  arise,  probably  in  the  skin  of  the  limb. 

Effect  of  Stimulating  the  Ends  of  Severed  Nerve  Roots.  —  If  we 
now  turn  to  the  roots  of  the  nerve,  and  make  similar  experiments,  we 
obtain  the  following  results  :  Stimulating  the  dorsal  root  causes  sensa- 
tion referred  to  some  outer  surface,  and  no  other  effect  is  noticed. 
Cutting  the  dorsal  root  also  causes  sensation.  Stimulating  the  end  of 
this  root  still  connected  with  the  spinal  cord  causes  sensation:  but 
stimulating  the  end  of  the  root  connected  with  the  nerve  gives  no 
appreciable  result. 

Stimulating  or  cutting  the  ventral  root  causes  motion  in  the  parts 
whose  muscles  are  supplied  by  fibers  from  this  root.  After  severing 
this  root,  if  the  end  connected  with  trie  spinal  cord  be  stimulated,  no 
effect  is  noticed ;  but  stimulating  the  end  still  connected  with  the  nerve 
is  followed  by  shortening  of  the  muscles  supplied. 

Effect  of  Severing  All  the  Spinal  Nerves.  —  Severing 
all  the  spinal  nerves  destroys  all  power  of  sensation  and 
voluntary  motion  in  all  parts  of  the  body  except  the  head. 
After  severing  all  the  dorsal  roots,  no  sensation  would  be 
produced  by  stimulating  any  part  of  the  body,  and  after 
severing  all  the  ventral  roots  no  act  of  the  will  can  cause 
any  of  the  muscles  of  the  body  to  act.  Severing  all  the 
nerves,  or  severing  all  the  roots,  cuts  off  all  communication 
of  the  brain  with  the  body,  and  so  far  as  motion  and  sensa- 
tion in  the  body  generally  are  concerned,  has  the  same 
effect  as  severing  the  spinal  cord  below  the  head. 


NERVOUS  SYSTEM.  35 

Cramp.  —  Cramp  is  a  spasmodic  shortening  of  the 
muscles,  attended  with  pain. 

Tetanus.  — Tetanus  (or  locked  jaw)  is  a  spasmodic  and 
continuous  shortening  of  the  muscles,  causing  rigidity  of 
the  parts  they  supply.  It  is  due  to  the  disordered  and 
excessive  stimulation  of  the  muscles  through  the  nerves. 

Crossing  of  the  Fibers  from  the  Brain  to  the  Spinal 
Cord.  —  Both  the  brain  and  the  spinal  cord  consist  of  two 
lateral  halves  connected  by  cross  fibers.  Each  half  of  the 
brain  is  connected  with  the  opposite  half  of  the  body. 
This  is  accomplished  by  the  crossing  of  the  fibers.  The 
fibers  that  carry  nerve  impulses  outward  are  now  known 
to  cross  as  they  leave  the  brain,  at  the  very  beginning  of 
the  spinal  cord,  in  the  part  known  as  the  spinal  bulb. 
The  sensations  arising  from  touching  anything  with  the 
right  hand,  therefore,  are  in  the  left  half  of  the  brain,  and 
the  right  half  of  the  brain  controls  the  left  hand. 

Voluntary  Interference  with  Reflex  Actions. — We 

have  seen  that  the  jerking  of  the  hand  away  from  a  hot 
object  is  due  to  reflex  action  of  the  spinal  cord.  One 
might,  by  a  powerful  effort  of  the  will,  keep  the  hand  on 
an  object  that  is  hot  enough  to  burn  the  skin.  One  may 
command  the  foot  to  remain  quiet  when  it  is  tickled ;  but 
as  soon  as  the  person  is  asleep,  the  same  stimulations 
would  be  followed  by  the  reflex  actions  such  as  we  have 
considered. 

In  these  cases  of  interference  it  is  understood  that  the 
brain  sends  a  nerve  impulse  down  to  the  centers  of  the 
reflex  action,  and  stops  or  diminishes  their  operation. 
This  retarding  influence  of  a  group  of  cells  is  called  inhi- 
bition. It  is  not  always  due  to  voluntary  interference, 
but  may  be  due  to  reflex  interference,  as  we  may  see  later. 


36  rHYSIOLOGY. 

The  Nature  of  a  Nervous  Impulse.  —  Of  the  nature 
of  a  nerve  impulse  we  know  but  little.  It  is  convenient 
to  compare  the  nervous  system,  with  its  conducting  fibers 
and  central  ganglia,  to  a  telegraph  system.  And  electric- 
ity is  the  most  convenient  stimulus  for  exciting  nerve  im- 
pulses. Yet  a  nerve  impulse  is  very  different  from  an 
electric  current.  A  nerve  fiber  is  a  poor  conductor  of 
electricity.  An  electric  current  may  travel  along  a  copper 
wire  at  the  rate  of  between  100,000  and  200,000  miles  a 
second,  while  a  nerve  impulse  in  a  motor  nerve  travels 
only  1 70  feet  in  a  second. 

Transmission  of  Motor  Impulses.  — When  a  motor  fiber  is  stimu- 
lated in  the  middle  of  its  course  we  observe  only  one  effect,  —  the 
shortening  of  the  muscle  at  its  lower  end.  But  there  is  every  reason 
to  believe  that  the  nerve  current,  or  impulse,  runs  along  the  nerve  in 
both  directions  from  its  starting  point.  But  while  the  action  of  the 
muscle  at  the  peripheral  extremity  manifests  the  existence  of  the  cur- 
rent, there  is  nothing  at  the  central  extremity  to  give  such  evidence. 

Transmission  of  Sensory  Impulses.  —  Similarly,  when  a  sensor 
nerve  fiber  is  stimulated  at  some  intermediate  point,  we  have  a  sensa- 
tion in  the  brain  due  to  the  current  brought  by  the  afferent  fiber,  and 
which  we  refer  to  the  outer  end  of  the  nerve  fiber.  Probably  a  nerve 
impulse  passed  from  the  point  of  stimulation  to  the  outer  end  of  the 
fiber ;  but  as  there  is  nothing  at  the  outer  end  of  the  nerve  fiber  to 
interpret  it,  we  get  no  evidence  of  such  impulse  except,  by  refined 
physiological  tests. 

Harmony  in  Muscle  Action.  —  In  throwing  a  stone  a 
number  of  muscles  are  used.  Each  one  of  these  must 
shorten  in  the  right  way  and  at  the  right  time  or  the  throw 
will  not  be  accurate.  Each  muscle  shortens  under  the 
influence  of  a  nerve  impulse  started  by  the  brain  and 
brought  by  a  motor  nerve.  If  any  muscle  shortens  an 
instant  too  soon,  or  a  little  too  strongly,  the  stone  goes  to 


NERVOUS  SYSTEM.  37 

one  side.  In  a  tune  on  a  piano  we  know  that  the  right 
keys  must  be  struck  ;  that  each  must  be  struck  at  the  right 
time,  with  the  proper  degree  of  force,  and  held  for  the 
right  length  of  time,  or  we  have  discord  instead  of  har- 
mony. What  the  player  is  to  the  instrument,  the  brain 
is  to  the  body. 

Temporary  Loss  of  Muscular  Power.  —  It  may  have 
happened  to  you  that  after  sitting  long  in  one  position  you 
attempted  to  stand,  but  found  that  you  could  not  do  so. 
One  leg  failed  to  act  at  the  bidding  of  your  will.  When 
the  foot  is  "  asleep  "  we  get  little  sensation  from  it ;  we 
hardly  know  whether  it  is  touching  the  floor  or  not.  Press- 
ing on  it  with  the  other  foot  causes  no  pain. 

We  try  to  stand  when  the  foot  is  asleep,  but  we  are 
unable  to  do  so.  The  brain  starts  the  nerve  currents,  and 
they  run  along  the  nerve  as  far  as  the  compressed  part ; 
here  they  stop.  They  cannot  reach  the  muscles  of  the 
leg  below.  Hence  the  muscles  do  not  shorten,  and  we 
do  not  rise,  no  matter  how  strongly  we  will  to  do  so. 

Why  is  it  that  the  nerves  and  muscles  thus  sometimes 
lose  their  ability  to  perform  their  natural  activities  ? 

Dependence  of  Nerves  and  Muscles.  —  This  has  been 
explained  by  saying  that  owing  to  external  pressure,  the 
nerve  has  temporarily  lost  its  power  of  conducting  nerve 
currents.  But  what  beside  the  nerve  has  been  com- 
pressed ?  What  process  in  the  limb  has  been  interfered 
with  by  the  pressure  due  to  the  position  in  which  one  has 
been  sitting  or  lying  ?  What  is  the  temperature  of  the 
benumbed  limb  ? 

On  what  are  the  nerves  and  muscles  so  dependent  for 
the  maintenance  of  their  activity  ? 


38  niYSioi.OGY. 

READING.  —  Power  through  Repose,  Call ;   The  Technique 
of  Rest,  Brackett;  Muscles  ami  Xerres^  Rosenthal. 


Summary.  —  I .    Motions  are  voluntary  or  involuntary,  but  all  are 
under  control  of  the  nervous  system. 

2.  The  cerebro-spinal  nervous  system  consists  of  the  brain,  the 
spinal  cord,  and  the  spinal  nerves. 

3.  Each  spinal  nerve  has  two  roots :  the  dorsal,  which  is  afferent 
and  sensory ;  the  ventral,  which  is  efferent  and  motor. 

4.  A  ganglion  is  a  nerve  center  largely  composed  of  nerve  cells. 

5.  Nerves  are  made  up  of  nerve  fibers. 

6.  A  nerve  fiber  consists,  of  the  central  core  (or  axis  cylinder), 
which  conducts  the  nerve  impulse,  the  medullary  sheath,  and,  outside, 
the  nerve-fiber  sheath. 

7.  The  spinal  cord  has  in  its  outer  part  white  nerve  fibers,  in  its 
center  gray  nerve  cells. 

8.  These  cells  are  branched,  and  at  least  one  branch  becomes  the 
axis  cylinder  of  a  nerve  fiber. 

9.  The  gray  matter  of  the  cord  is  the  center  of  the  reflex  action. 

10.  The  nerve  fibers  from  each  half  of  the  brain  connect  with  the 
opposite  half  of  the  body. 

11.  The  nervous  system  is  comparable  to  a  telegraph  system. 

Questions.  —  i.    Name  as  many  involuntary  motions  as  you  know. 

2.  What  other  cases  of  reflex  action  do  you  know  ? 

3.  The  story  is  told  of  a  young  Roman  (Mucius  Scaevola)  that  to 
show  his  fortitude  he  thrust  his  hand  into  the  fire  and  held  it  there 
until  it  was  destroyed.     What  physiological  action  does  this  illustrate  ? 

4.  Why  is  a  man  partially  paralyzed  when  he  has  broken  his  neck 
or  back  ? 

5.  How  does  the  nervous  system  differ  from  a  telegraph  system? 


CHAPTER   IV. 
CIRCULATION  OF  THE  BLOOD. 

The  Blood  and  its  Work.  —  We  know  that  if  any  animal 
is  bled  freely,  it  soon  becomes  weak,  then  unconscious,  and 
soon  dies,  if  the  escape  of  blood  be  not  stopped. 

We  observe  the  natural  difference  in  color  of  different 
parts  of  our  bodies ;  for  instance,  the  lips  and  cheeks. 
We  often  note  varying  color,  as  in  blushing  and  pallor. 

We  wish  to  understand  these  differences  and  changes ; 
also  to  know  what  to  do  in  case  of  fainting  or  bleeding 
from  wounds.  We  may  prolong  and  make  more  useful 
our  own  lives  and  those  of  others  by  knowing,  in  a  practical 
way,  something  about  the  causes,  prevention,  and  remedies 
of  the  colds,  congestions,  and  inflammations  to  which  we 
are  subject. 

Nearly  every  part  of  the  body  bleeds  when  cut.  There 
is  no  bleeding  when  we  trim  the  nails  or  cut  the  hair,  and 
the  outer  skin  has  no  blood  in  it.  But  the  inner  skin,  and 
almost  every  tissue  within  it,  if  pierced  even  by  the  finest 
needle,  yields  blood.  We  see  a  little  blood  oozing  from 
the  surface  of  a  fresh  steak  or  roast. 

What  kind  of  a  substance  is  the  blood  ?  Is  it  uniformly 
distributed  through  the  tissues,  like  water  soaked  up  into  a 
cloth,  or  is  it  in  distinct  cavities  ?  Why  is  it  so  essential  to 
life  ?  How  does  it  do  its  work  ? 

The  Rate  of  the  Heart  Beat.  — The  heart  beats  about 
seventy-two  times  a  minute  in  men ;  in  women,  about 

39 


4O  PHYSIOLOGY. 

eighty.  At  birth  the  rate  is  from  one  hundred  and  thirty 
to  one  hundred  and  forty,  and  gradually  decreases  till 
about  the  age  of  twenty,  when  the  average  of  seventy-two 
is  reached.  This  rate  holds  till  old  age,  when  it  increases. 
The  rate  is  increased  by  muscular  activity,  food,  external 
heat,  internal  heat  (fever),  pain,  and  mental  excitement. 
Music  accelerates  the  pulse  rate.  The  pulse  rate  varies 
during  the  twenty-four  hours,  being  lowest  during  the 
night,  and  highest  about  1 1  A.M.  Certain  diseases  increase 
the  frequency  of  the  pulse.  Some  drugs  quicken  the 
pulse  rate,  and  others  dimmish  it. 

The  Heart  Beat  and  the  Pulse.  —  i .  The  heart  beat,  felt  at  the  left 
of  the  breast  bone. 

2.  The  pulse,  felt  at  the  wrist  and  at  various  parts  of  the  body. 
Perhaps  the  most  convenient  place  to  study  it  is  at  the  temple.  Lay 
the  forefinger  lightly  along  the  cheek  just  in  front  of  the  ear.  Count 
the  pulsations  for  a  minute. 

Let  one  or  two  pupils  who  are  quick  at  figures  step  to  the  blackboard 
and  put  down  the  number  of  pulsations  of  each  pupil,  and  divide  by  the 
number  thus  reporting,  to  get  the  average. 

1 .  Let  all  in  the  class  count  the  pulse  while  sitting.     Probably  it 
will  be  best  to  discard  the  first  trial,  as  there  are  likely  to  be  several 
failures  from  one  cause  or  another.     Then,  too,  there  is  usually  a  slight 
excitement  at  the  beginning  of  a  wholly  new  experiment.    Get  the  aver- 
age of  the  class. 

2.  Find  the  pulse  while  sitting;  rise  quickly,  and  immediately  begin 
to  count  the  pulse.     Compare  with  the  pulse  as  taken  while  sitting. 

3.  Compare  the  pulse  before  and  after  meals. 

4.  With  the  thumb  and  finger  lightly  clasp  the  windpipe,  well  back. 
The  pulse  in  the  carotid  arteries  will  be  felt. 

The  Position  of  the  Heart.  —  The  base  of  the  heart  is 
in  the  center  of  the  chest,  just  back  of  the  breast  bone,  but 
the  apex  points  downward  and  to  the  left. 

The  Covering  of  the  Heart.  —  The  heart  is  inclosed  in 
a  loosely  fitting  membranous  bag,  the  pericardium.  Within 


CIRCULATION  OF  THE  BLOOD.  41 

the  pericardium  and  around  the  heart  ivS  a  small  quantity 
of  liquid,  called  the  pericardial  fluid. 

The  Size  of  the  Heart.  — A  person's  heart  is  about  the 
size  of  his  clenched  hand. 

The  External  Features  of  the  Heart.  — The  heart  is 
cone-shaped  and  the  bulk  of  it  is  made  up  of  the  ventricles, 
the  auricles  being  two  ear-like  flaps  at  the  base,  one  on 
each  side.  There  is  a  deep  notch  between  the  auricles 
and  the  ventricles.  The  line  of  division  between  the  two 
ventricles  is  marked  by  a  groove,  which  runs  obliquely 
along  the  ventral  surface.  In  this  groove  are  blood  tubes 
and  usually  considerable  fat. 

The  Internal  Structure  of  the  Heart.  —  The  two  halves 
of  the  heart  are  completely  separated  from  one  another 
by  a  partition.  Each  half,  in  turn,  has  valves  which, 
part  of  the  time,  separate  the  cavity  of  each  auricle  (at 
the  base)  from  the  cavity  of  the  corresponding  ventricle 
(at  the  apex). 

The  Valves  of  the  Heart.  —  Between  the  auricles  and 
the  ventricles  are  curtain-like  valves,  whose  upper  edges 
are  attached  to  the  inner  surface  of  the  walls  at  the  upper 
margin  of  the  ventricle.  These  flaps  are  somewhat  tri- 
angular, and  have  strong  white,  tendinous  cords  extending 
from  their  edges  and  under  surfaces  to  the  walls  of  the 
ventricle  below.  In  the  right  half  of  the  heart  there  are 
three  flaps,  and  this  valve  is  called  the  tricuspid  valve.  In 
the  left  side  there  are  two  flaps,  which,  together,  constitute 
the  mitral  valve.  In  the  resting  heart  these  flaps  hang 
down  along  the  walls  of  the  ventricles  so  that  on  opening 
the  heart  one  would  see  only  a  single  cavity  in  each  half 
of  the  heart. 


42 

The  Semilunar  Valves.  —  From  the  base  of  the  right 
ventricle  arises  the  pulmonary  artery.  Within  its  base, 
just  as  it  leaves  the  ventricle,  are  three  pocket-like  valves, 
like  "  patch-pockets."  They  are  in  a  circle,  with  their  edges 
touching,  and  thus  surround  the  opening,  with  their 
mouths  opening  away  from  the  heart.  A  similar  set  of 
valves  are  within  the  base  of  the  aorta,  which  arises  from 
the  left  ventricle.  Both  these  sets  of  valves  are  called 
semilunar  valves. 

Dissection  of  the  Heart.  —  No  description  (nor  even  figures)  can 
give  a  clear  idea  of  the  heart.  A  good  model  will  be  of  some  assist- 
ance. But  the  heart  itself  should  be  examined  carefully  and  then  dis- 
sected. The  heart  and  lungs  of  a  sheep  should  be  obtained  (ask  the 
butcher  to  save  the  "pluck,"  i.e.  the  heart  and  lungs  taken  out  together). 
The  relations  of  the  heart  to  the  lungs  and  other  organs  should  first 
be  studied,  and  then  the  pericardium  opened.  Observe  the  outside  of 
the  heart,  and  then  cut  the  heart  open  to  see  the  points  given  in  the 
above  description.  After  the  heart  is  severed  from  the  lungs  the  auri- 
cles may  be  cut  off;  then,  by  pouring  water  into  the  ventricle,  the 
action  of  the  valves  between  the  auricles  and  the  ventricles  will  be 
seen.  Pressing  on  the  outer  surface  of  the  right  ventricle  will  make 
the  water  escape  through  the  pulmonary  artery.  If  this  be  split  open, 
the  semilunar  valves  at  its  base  may  be  found. 

The  Blood  Tubes  connecting  the  Heart  with  Other 
Organs.  —  The  aorta  (the  largest  artery  in  the  body) 
arises  from  the  base  of  the  left  ventricle,  and  supplies 
with  blood  every  organ  of  the  body  except  the  lungs. 
The  pulmonary  artery  springs  from  the  base  of  the  right 
ventricle  and  sends  blood  to  the  right  and  left  lungs. 
Two  large  veins  enter  the  right  auricle,  the  precaval  vein 
from  the  anterior  regions  of  the  body  and  the  postcaval 
vein  brings  blood  from  all  the  organs  of  the  posterior  por- 
tions of  the  body.  The  pulmonary  veins  return  the  blood 
from  the  lungs  to  the  left  auricle,  two  from  each  lung. 


CIRCULATION  OF  THE  BLOOD. 


43 


44 


PHYSIOLOGY. 


fL   External  Jugular  Vein 

Internal  Jugular  Vein 


2  Subclavian  Artery 
b  Subclavian  Vein 
1   Carotid  Artery 


i  Aorta 
in  Precaval  Vein 


IV   Postcaval  Vein 


Gastric  Artery 
Splenic  Artery 
Hepatic  Artery 
Pancreatic  Artery 


ff  Renal  Veins 
5  Renal  Arteries 


T  Iliac  Arteries 
i  Iliac  Veins 


Fig.  16.    Distribution  of  Arteries  and  Veins. 


CIRCULATION  OF  THE  BLOOD. 


45 


The  Distribution  of  the  Arteries  and  Veins.  —  The 

organs  of  the  body  receive  a  supply  of  blood  in  propor- 
tion to  their  size  and  activity.  The  artery  supplying  the 
blood  and  the  vein  which  returns  it  usually  lie  side  by  side 
(see  Fig.  16).  The  larger  arteries  are  usually  deep-seated 
and  in  protected  places. 

Demonstration  of  the  Action  of  the  Heart.  —  The  heart  may  be 
mounted  as  shown  in  Fig.  17,  and  its  action  illustrated  by  compressing 
the  ventricles  with  both  hands.  Instead  of  the  apparatus  here  shown 
two  retort  stands  may  be  used,  though  not  so  convenient. 


Capillaries 
of  the  Lungs 


Capillaries 
of  the  Body 


Fig.   17.    Demonstration  of  the  Action  of  the  Heart  (Heart  Diagrammatic). 


The  Action  of  the  Heart.  -  -  The  -heart  consists  of 
muscle  fibers  so  arranged  that  they  form  a  thick-walled 
bag,  which  stands  expanded  when  the  muscles  relax.  But 
when  the  fibers  shorten  the  whole  heart  contracts,  and  the 


46  PHYSIOLOGY. 

cavity  is  much  reduced  in  size,  if  not  entirely  obliterated, 
and  the  blood  is  forced  out. 

The  complete  action  of  the  heart  consists  of  three  parts, 
—  the  contraction  of  the  auricles,  the  contraction  of  the 
ventricles,  and  the  pause. 

The  Pause.  —  During  the  pause  the  blood  is  steadily 
pouring  into  the  auricles ;  into  the  right  auricle  from  the 
caval  veins,  into  the  left  auricle  from  the  pulmonary  veins. 
At  this  time  the  curtain-like  valves  between  the  auricles 
and  the  ventricles  are  open,  and  their  flaps  hang  loosely 
beside  the  walls  of  the  ventricles.  The  blood,  therefore, 
as  it  passes  into  the  auricles,  passes  on  into  the  ventricles. 
As  the  ventricle  fills,  the  valves  float  up,  as  seen  in  the 
experiment  of  pouring  water  into  the  ventricle. 

The  Contraction  of  the  Auricle.  —  When  the  ventricle 
is  full,  but  not  stretched,  and  the  auricle  partly  full,  the 
auricle  suddenly  contracts,  thus  forcing  more  blood  into 
the  ventricle,  and  distending  it.  At  the  same  time  the 
valves,  which  were  already  nearly  closed,  are  tightly  closed 
by  the  pressure  of  the  blood  which  is  forced  up  behind 
them.  The  flaps  of  the  valves  are  kept  from  going  up  too 
far  by  the  tendinous  cords  and  by  the  papillary  muscles  to 
which  the  cords  are  attached. 

The  Contraction  of  the  Ventricle.  —  Next  comes  the 
contraction  of  the  ventricle,  slower,  but  more  powerful 
than  that  of  the  auricle.  As  the  walls  of  the  ventricle  are 
drawn  together,  the  blood  is  subjected  to  pressure.  It 
cannot  go  back  into  the  auricles,  for  the  more  it  presses 
against  the  valves,  the  more  tightly  they  are  closed.  The 
semilunar  valves  are  closed  by  back  pressure  in  the  aorta 
and  pulmonary  artery.  But  the  pressure  of  the  blood  in 
the  ventricles  is  so  much  greater  that  the  semilunar  valves 


CIRCULATION  OF  THE  BLOOD, 


47 


are  forced  open,  and  nearly  all  the  blood  is  driven  out  of 
the  ventricles ;  from  the  right  ventricle  into  the  pulmonary 
artery,  and  from  the  left  ventricle  into  the  aorta. 

While  the  ventricles  are  contracting  and  forcing  their 
blood  out,  the  auricles  are  slowly  filling  by  the  steady 
inflow  through  the  veins. 

Systole  and  Diastole.  —  The  contraction  of  the  heart  is 
called  the  systole,  and  its  dilation  the  diastole. 

Dilation  of  the  Ventricle.  —  As  soon  as  the  ventricle 
has  completed  its  contraction  it  dilates,  and  most  of  the 
blood  that  has  accumulated  in  the  auricle  simply  falls  into 
the  ventricle.  The  dilating  ventricle  exerts  a  slight  suc- 
tion, so  the  blood  is  in  part  drawn  into  the  ventricle.  Dur- 
ing the  remainder  of  the  pause  the  blood  accumulates  in 


Auricle 


Fig.  1 8.     Diagram  of  the  Heart,  showing  the  Action  of  the  Valves. 

the  auricle  and  ventricle  till  the  auricle  again  contracts  and 
the  cycle  is  repeated.  This  is  true  of  both  halves  of  the 
heart,  which  work  simultaneously,  the  right  heart  pumping 
dark  blood  while  the  left  heart  pumps  bright  blood.  The 
left  ventricle  is  thicker  walled  and  stronger  than  the  right. 


48  PHYSIOLOGY. 

Work  and  Rest  of  the  Heart.  —  The  time  taken  by  the 
different  parts  of  the  heart  beat  are  about  as  follows :  The 
auricle  contracts  about  one  eighth  of  the  time  and  rests 
the  other  seven  eighths.  The  ventricle  contracts  about 
three  eighths  of  the  time  and  dilates  during  about  five 
eighths.  If  we  suppose  the  whole  period  of  the  heart  beat 
to  be  twenty-four  hours  (instead  of  eight  tenths  of  a  sec- 
ond), we  can  more  easily  see  how  much  of  the  time  the 
heart  is  actually  at  work,  and  how  much  of  the  time  the 
heart  is  resting. 

Auricle      contracting  (working)  \  of  the  time  —  3  h.,  resting  21  h. 
Ventricle  contracting  (working)  f  of  the  time  —  9  h.,  resting  15  h. 

No  part  of  the  heart,  therefore,  is  working  longer  than  a 
man  would  who  only  works  nine  hours  a  day.  Some  ob- 
servers state  that  the  resting  period  is  even  greater  than 
these  figures  would  show. 

Since  the  contraction  of  the  ventricles  immediately  fol- 
lows that  of  the  auricles,  one  half  of  the  time  is  occupied 
by  the  whole  contraction  of  the  heart,  and  during  half  the 
time  the  whole  heart  is  resting.  This  is  different  from  our 
usual  statements  regarding  the  work  of  the  heart.  We 
hear  it  said  that  the  heart  never  rests.  Its  work  and  rest 
follow  each  other  at  such  short  intervals  that  we  do  not 
appreciate  the  interval  of  rest  that  comes  between  the  suc- 
cessive impulses  that  we  feel.  Suppose  a  policeman  had 
the  power  of  sleeping  at  will,  and  that  he  slept  thirty  min- 
utes of  each  hour,  and  that  in  the  remaining  thirty  minutes 
he  made  the  rounds  of  a  block.  If  we  saw  him  passing 
regularly  once  an  hour,  every  hour  of  the  twenty-four,  we 
might  suppose  that  he  did  not  sleep  at  all  during  the  entire 
time.  This  ratio  of  work  and  rest  is  fairly  constant  in 
the  varying  rates  of  heart  beat. 


CIRCULATION  OF  THE  BLOOD. 


49 


The  Beat  of  the  Heart.  —  The  apex  of  the  heart  is 
always  in  contact  with  the  chest  wall.  Consequently,  it 
never  strikes  it.  At  each  beat  it  pushes  hard  against  the 
chest  wall.  This  push  may  be  felt  and  seen,  and  is  called 
the  heart  beat. 

The  Sounds  of  the  Heart.  —  There  are  two  sounds  of 
the  heart :  — 

1.  A  short,  sharp  sound  made  by  the  closing  of  the  semi- 
lunar  valves. 

2.  Just  preceding  this  sound  a  longer,  duller  sound  may 
be  heard  during  the  contraction  of  the  ventricles.     This  is 
supposed  to  be  due  to  the  vibrations  of  the  walls  of  the 
ventricles  and  of  the  large  valves. 


As  soon  as 


Nucleus 


Isolated  Fibers 


Fibers  Joined 


Action  of  the  Large  Arteries.  —  The  large  arteries 
have  in  their  walls  a  yellow  elastic  tissue.  When  the 
blood  is  forced  into  them,  they  are  stretched, 
the  ventricle  ceases  to  contract, 
and  sends  no  more  blood  into 
the  arteries,  they  "stretch  back." 
We  should  not  say  contract,  for 
it  is  simply  an  elastic  reaction. 
As  the  artery  reacts  it  presses  on 
the  blood,  and  hence  the  blood 
tries  to  escape  in  every  possible 
way.  It  cannot  go  back,  for  it 
fills  the  pockets  of  the  semilunar 
valves,  and  closes  them  with  a 
click.  A  rapid  wave  is  sent  for- 
ward that  gives  the  pulse,  and  a  slower  but  still  rapid 
stream  flows  along  the  arteries,  through  the  pulmonary 
artery  to  the  lungs,  and  through  the  aorta  and  its  branches 
to  all  the  other  parts  of  the  body. 


Fig.  1 9.     Plain  (Unstriated)  Muscu- 
lar Fibers  from  the  Bladder. 


50  PHYSIOLOGY. 

The  elastic  reaction  of  the  arteries  thus  helps  to  make 
steady  the  flow  of  blood,  which  is  intermittent  as  it  leaves 
the  heart.  The  medium-sized  arteries  also  have  elastic 
tissue  in  their  walls,  and  regulate  the  blood  flow  in  the 
same  way. 

Variation  of  the  Amount  of  Blood  Needed.  —  Each 
organ  requires  a  supply  of  blood  in  proportion  to  its 
activity.  An  actively  working  organ,  like  the  brain,  de- 
mands much  more  blood  than  bone,  practically  inactive. 
Further,  working  tissues,  such  as  the  brain  and  muscles, 
need  a  great  deal  more  blood  while  they  are  at  work  than 
when  they  are  resting.  An  organ  needing  a  constant  large 
supply  of  blood  might  secure  this  by  having  a  large  artery. 
But  how  can  the  supply  be  regulated  so  that  an  organ 
may  receive,  now  more,  now  less,  according  to  its  needs  ? 

Plain  Muscle  Fibers  in  the  Walls  of  the  Arteries.  — 
This  is  regulated  by  the  medium-sized  and  small  arteries 

Connective  Tissue 


Endothelium  


Muscle  Fiber 


Fig.  20.    Plain  Muscle  Fiber.    Isolated  and  in  Wall  of  Artery. 

leading  to  the  parts.     In  the  walls  of  these  arteries  are 
muscle  fibers  of  a  different  kind  from  those  of  the  skele- 


CIRCULATION  OF  THE  BLOOD.  51 

ton.  These  fibers  are  spindle-shaped  cells,  as  shown  in 
Fig.  19,  with  a  nucleus  near  the  center,  and  do  not  have 
the  cross-markings  of  the  fibers  of  the  skeletal  muscles  ; 
they  are  in  consequence  called  nonstriated,  smooth,  or 
plain  muscle  fibers.  They  are  arranged  circularly  in  the 
walls  of  the  arteries.  These  fibers  have,  in  common  with 
all  muscle  fibers,  the  power  of  shortening.  When  they 
shorten  they  reduce  the  size  of  the  artery,  and,  there- 
fore, for  the  time,  less  blood  can  flow  through  the 
artery.  When  the  muscle  fibers  cease  to  shorten,  the 
artery  widens,  and  allows  more  blood  to  pass  through  it. 

Illustration  of  the  Action  of  Muscles  in  Arterial  Walls.  — To 

illustrate  the  action  of  the  muscles  in  the  walls  of  an  artery,  let  the 
water  run  through  a  hose  or  large 
rubber  tube.     Now,  if  a  row  of  per- 
sons take  hold  of  this  tube,  the  grip         Endotheiium 

of  their   hands  is  like  that  of  the 

muscles.     When  the  hands  tighten     internal  Elastic  — 

their  grip,  the  caliber  of  the  hose        Layer 

or  tube  is  diminished,  and  less  water 

is  allowed  to  flow  through  it.    When       Circular  Mus- 
cle Fibers 
the    hands    relax,    the    tube,   being 

elastic,  allows  more  liquid  to  flow 
through  it. 

Illustration  of  a  Small  Artery. 

—  To  represent  a  small  artery,  take 
a  small,  thin-walled  rubber  tube  and 
wind  a  red  thread  around  it.  Now, 

if    the    thread     could     be     made     to          Fl*  21-     Coats  of  a  Small  Artery. 
shorten,  it  would  diminish  the  cali- 
ber of  the  tube.     The  representation  would  be  more  exact  if  the  thread 
were  cut  into  many  short  pieces,  and  if  each  piece  were  thicker  in 
the  middle,  and  were   then  glued   to  the   tube.     If  the  whole  were 
covered  by  a  layer  of  tissue  paper,  the  structure  of  the  artery  would  be 
roughly  represented. 


52  PHYSIOLOGY. 

Plain  and  Striated  Muscle  Fibers  Compared.  —  These  plain  mus- 
cle fibers  are  further  like  those  of  the  skeletal*muscles  in  that  they  are 
under  the  control  of  the  nerves,  but  they  are  involuntary  in  their  action. 


PIGMENT 
CELLS 


ARTERY 
Fig.  22.    Part  of  Frog's  Web  (low  magnifying  power). 

We  cannot  interfere  with  the  action  of  these  muscles,  no  matter  how 
strongly  we  may  will  to  do  so.     Without  our  thinking  about  it,  more 


CIRCULATION  OF  THE  BLOOD. 


53 


blood  goes  to  the  muscles  of  the  legs  when  we  walk,  more  to  the  brain 
when  we  are  studying,  to  the  digestive  organs  after  eating,  etc.     The 


Walls  of  Capillari 


Tissues  of  Web 


£     \ 


Fig.  23.     Part  of  Frog's  Web  (highly  magnified). 

plain  muscle  fibers  shorten  at  a  much  slower  rate  than  the  striated 
fibers.  They  are  also  slower  in  relaxing.  Since  the  plain  muscles  are 
usually  found  in  the  walls  of  hollow  organs  such  as  the  heart,  blood 


54 


PHYSIOLOGY. 


tubes,  digestive  tube,  etc.,  they  are  sometimes  called  visceral  muscles  in 
distinction  from  the  skeletal  muscles. 

The  Circulation  of  Blood  in  the  Web  of  a  Frog's  Foot.  —  For  this 
get  a  frog  with  a  pale  web.  Take  a  piece  of  shingle  six  inches  long 
and  three  inches  wide.  Cut  a  round  hole,  half  an  inch  in  diameter, 
near  one  end  of  it.  Wrap  the  frog  in  a  wet  cloth,  with  one  leg  project- 
ing, and  tie  it,  thus  wrapped,  to  the  shingle.  Tie  threads  around  two 
of  the  toes,  and  stretch  the  web,  but  not  too  tightly,  over  the  hole. 
Keep  the  web  moist.  Place  the  shingle  firmly  on  the  stage  of  a  micro- 
scope. Examine  first  with  a  low  power.  The  large  tubes  which  grow 
smaller  by  subdivision  are  arteries.  The  large  tubes  which  are 
formed  by  the  union  of  smaller  ones  are 
the  veins.  The  finer  tubes,  forming  a  net- 
work in  every  direction,  are  the  capillaries. 
They  receive  the  blood  from  the  arteries 
and  pass  it  on  to  the  veins. 

Put  on  a  higher  power,  a  one-fifth  or 
one-sixth  objective.  It  may  now  be  seen 
that  the  colored  corpuscles  float  more  in 
the  center  of  the  stream,  and  with  a  steady 
motion,  while  the  colorless  corpuscles  keep 
close  to  the  walls  of  the  capillary,  and  seem 
to  adhere  to  them,  advancing  with  a  hesi- 
tant motion,  seeming  to  roll  along  against 
the  wall  of  the  capillary. 

Close  your  eyes  for  a  moment,  and  re- 
flect that  in  all  the  active  tissues  of  your 
body  —  for  example,  the  muscles,  brain,  and 
digestive  organs  —  there  is  a  similar  net- 
work of  fine  tubes  with  a  current  of  blood 

running  through  them.  The  current  is  not  so  rapid  as  it  seems,  for  the 
microscope  magnifies  the  rate  of  flow  as  well  as  the  size  of  the  cor- 
puscles. The  blood  really  is  moving  slowly  in  the  capillaries,  and  it  is 
very  important  that  it  should  be  so,  for  in  the  capillaries  the  work  of 
the  blood  is  done.  Part  of  the  liquid  of  the  blood  soaks  through  the 
thin  walls  of  the  capillaries,  and  nourishes  the  surrounding  tissues.  All 
the  other  parts  of  the  circulatory  system  exist  for  the  purpose  of  send- 
ing a  continuous,  slow,  and  steady  stream  of  blood  through  the 
capillaries.  (See  pages  72  and  73.) 


Fig.  24-     Capillary  Blood 
Tubes  of  Muscle. 


CIRCULATION  OF  THE  BLOOD. 


55 


Connective 

Tissuf 


Artery 


Fig.  25. 


Cross-section  of  Small  Artery 
and  Vein. 


The  Blood   Flow  in  the   Capillaries.  —  The  arteries 

divide  and  subdivide,  and  become  capillaries,  which  have 

connecting  branches,  form- 
ing a  close  network  of  tiny 
thin-walled  tubes.  These 
penetrate  nearly  every  tis- 
sue of  the  body.  The  blood 
cannot  do  its  full  work  till  it 
is  in  the  tissues/and  to  reach 
the  tissues  it  must  soak 
through  the  walls  of  the 
capillaries.  The  work  of 
the  heart  and  arteries  is  to 
keep  a  steady  flow  of  blood 

through  the  capillaries,  that  the  tissues  may  be  constantly 

supplied. 

How  is  it  that  the  jerky  action  of  the  heart,  at  each 

contraction  sending  a  jet  of 

blood   into   the   arteries,  — 

shown  by  a  spurt  when  an 

artery  is  severed,  and  also 

indicated    by   the   intermit- 
tent   pulse,  —  how    is    this 

intermittent  flow  converted 

into    the     steady,    uniform 

current  that  we  have  seen 

in  the  capillaries  ? 

Experiments  illustrating  the 
Blood  Flow  in  the  Capillaries.— 

A  few  experiments  may  make  this     Fig.  26. 


Surface  View 


Longitudinal  Section 


matter  more  clear. 


Capillaries,  composed  of  a  single 
layer  of  cells. 

Material :  —  i .    A  common  rubber  syringe. 

2.   A  glass  tube  three  feet  long  and  seven  sixteenths  of  an  inch 
outside  diameter. 


56  PHYSIOLOGY. 

3.  Four  inches  of  the  same  size  glass  tubing,  for  making  connec- 
tions. 

4.  Several  nozzles,  made  of  the  same  size  glass  tubing,  all  fine,  but 
of  varying  degrees  of  fineness. 

5.  India-rubber  tubing,  twelve  feet,  three  eighths  of  an  inch  inside 
diameter.     This  should   be  black,  pure  gum,  rubber  which  is   more 
highly  elastic  than  the  other  kinds. 

6.  Three  feet  of  rubber  tubing,  same  size  as  above. 

7.  Four  inches  of  white  rubber  tubing,  same  size  as   above,  for 
making  connections. 

In  all  the  experiments,  have  one  of  the  students  assist  by  holding 
the  outlet  tube,  so  that  (i)  all  the  members  of  the  class  may  see  the 
stream,  and  (2)  that  the  stream  may  be  suitably  directed,  as  into  a  pail 
or  sink. 

Count  aloud,  to  mark  the  exact  time  of  each  compression  of  the 
bulb,  so  the  students  can  compare  this  with. the  time  and  duration  of 
the  jets  of  water. 

Be  very  careful  to  use  perfectly  clean  water,  as  any  fine  particles  of 
sediment  drawn  into  the  tube  are  likely  to  clog  the  fine  outlet  of  the 
nozzle.  And  it  is  well  to  take  the  further  precaution  not  to  let  the 
supply  tube  touch  the  bottom  of  the  water-supply  dish,  as  some  fine 
sediment  may  get  in  in  spite  of  previous  care. 

EXPERIMENT  i.  — Remove  the  nozzle  of  the  syringe,  and  put  in  its 
place  the  long  glass  tube.  Work  the  syringe,  and  note  that  the  jet  is 
jerky,  following  each  contraction  of  the  bulb. 

EXPERIMENT  2.  —  Substitute  the  rubber  tube,  three  feet  long,  for 
the  glass  tube.  On  working  the  bulb  the  stream  will  be  found  inter- 
mittent. 

EXPERIMENT  3.  — Take  off  the  rubber  tube  and  replace  the  glass 
tube,  adding  the  nozzle.  Here  the  pressure  will  be  so  great  that  it  is 
likely  to  push  off  the  nozzle  unless  the  assistant  holds  it  firmly.  It 
could  be  tied  on,  but  this  takes  more  time.  On  working  the  bulb, 
greater  effort  must  be  made  on  account  of  the  resistance  caused  by  the 
narrower  outlet. 

EXPERIMENT  4.  —  Once  more  substitute  the  rubber  tube,  this  time 
with  a  glass  nozzle  in  its  end.  Now,  on  working  the  bulb,  resistance 
will  be  felt,  and  the  stream  will  be  constant,  or  nearly  so,  and  will  con- 
tinue for  some  time  when  the  bulb  is  no  longer  worked.  This  is  be- 
cause the  rubber  has  been  stretched,  chiefly  laterally,  and  is  now 


CIRCULATION  OF  THE  BLOOD. 


57 


"  stretching  back."  That  is,  by  the  elastic  reaction  of  the  rubber  tube 
the  jerky  action  of  the  bulb  is  converted  into  the  steady  flow  that  we 
see.  In  the  first  experiment  we  had  a  rigid  tube  and  practically  no 
resistance.  In  the  second,  although  the  tube  was  elastic,  there  was  no 
resistance,  so  the  elasticity  was  not  brought  into  play.  In  the  third, 
there  was  resistance,  but  the  tube  was  inelastic.  In  the  fourth,  the 
resistance  brought  into  play  the  elasticity  of  the  rubber  tube,  and  the 
elastic  reaction  of  the  tube  continues  (so  to  speak)  the  action  of  the  bulb 
between  two  successive  strokes.  In  this  experiment  the  pulse  can  be 
felt  in  the  tube. 

The  Veins.  —  The  capillaries,  after  penetrating  the  tis- 
sues, reunite  to  form  small  veins,  which  in  turn  reunite 
to  form  larger  ones,  till  finally  two  great  veins,  the  caval 
veins,  precaval  and  postcaval,  return  the  blood  to  the 
heart.  The  veins,  like  the  arteries,  are  smooth  inside  and 
elastic  (though  less  elastic  than  the  arteries).  They  are 
thinner  than  the  arteries,  and,  in  consequence,  collapse 
when  the  blood  flows  out  of  them,  whereas  the  larger 
arteries  stand  open,  after  they  are  emptied  of  blood. 

The  Valves  in  the  Veins.  —  The  only  valves  in  the  arte- 
ries are  those  which  we  have  seen  at  the  beginning  of  the 
aorta  and  pulmonary  artery. 
Many  of  the  veins  have 
similar  pocket-like  valves, 
though  less  strong  than 
those  of  the  arteries.  They 
are  usually  in  pairs,  but  some- 
times single  or  in  threes.  It 
is  important  to  note  that  they 
all  have  the  mouths  of  the 
pockets  toward  the  heart,  so 
that  the  blood  flows  freely 
toward  the  heart,  but  is  prevented  from  flowing  the  other 
way  on  account  of  the  filling  of  the  valves  by  the  reflow 


Open  Shut 

Fig.  27.    Venous  Valves. 


58  PHYSIOLOGY. 

of  the  blood  stream.  When  the  blood  is  flowing  through 
the  veins  toward  the  heart  the  valves  lie  against  the  walls 
of  the  veins. 

The  valves  are  most  numerous  in  the  medium-sized  veins, 
and  especially  in  the  veins  of  the  extremities ;  more  abun- 
dant in  the  leg  than  in  the  arm.  Valves  are  absent  from  the 
caval  and  some  other  veins,  and  from  the  very  small  veins. 

Illustration  of  Venous  Valves.  — Make  a  cloth  tube  (or  take  the 
lining  of  a  boy's  coat  sleeve)  and  sew  three  patch-pockets  on  the  in- 
side, in  a  circle,  i.e.  with  edges  touching  each  other.  Make  the  pockets 
a  little  "  full."  Pour  sand,  shot,  or  grain  through  the  sleeve  first  in 
one  direction  and  then  in  the  other. 

Evidences  of  Valves  in  our  Veins.  —  With  the  forefinger  stroke 
one  of  the  veins  on  the  hand  or  wrist  toward  the  tips  of  the  fingers. 
The  veins  swell  out.  The  blood  meets  resistance  in  the  valves  of  the 
vein.  Their  location  may  be  determined  by  their  bulging  out  during 
the  experiment. 

Stroke  a  vein  toward  the  body,  and  the  blood  is  pushed  along  with- 
out resistance. 

Let  the  left  hand  hang  by  the  side.  Note  the  large  vein  along  the 
thumb  side  of  the  wrist.  Place  the  tip  of  the  second  finger  on  this 
vein  just  above  the  base  of  the  thumb.  Now,  while  pressing  firmly 
with  the  tip  of  the  second  finger,  let  the  forefinger,  with  moderate 
pressure,  stroke  the  vein  up  the  wrist.  It  may  be  seen  that  the  blood 
is  pushed  on  freely,  but  comes  back  only  part  way.  It  stops  where  it 
reaches  the  valves,  filling  the  vein  full  to  this  point,  but  leaving  it  col- 
lapsed beyond,  as  shown  by  the  groove.  Remove  the  second  finger, 
and  the  vein  immediately  fills  from  the  side  nearer  the  tip  of  the  fingers. 

These  experiments  show  that  the  blood  in  the  veins  moves  freely 
toward  the  body,  but  cannot  flow  outward  to  the  extremities. 

Dissection  of  the  Valves  in  a  Vein.  —  The  valves  may  be  seen  by 
dissecting  out  the  jugular  vein  (or  any  other  large  superficial  vein)  of  a 
cat,  dog,  or  rabbit.  Split  the  vein  and  pin  it  out  on  a  board. 

Effect  of  Pressure  on  the  Veins.  —  Since  the  valves  in 
the  veins  open  toward  the  heart,  any  intermittent  pressure 
on  the  veins  helps  to  push  the  blood  on  toward  the  heart. 


CIRCULATION  OF  THE  BLOOD.  59 

The  valves  are  most  numerous  in  the  superficial  veins  and 
those  of  the  muscles.  The  pressure  of  the  muscles  during 
their  action  (thickening  while  shortening)  produces  pres- 
sure on  the  veins ;  and  as  the  muscles  act  for  a  short  time 
only,  and  then  relax,  this  alternate  compression  and  release 
aids  very  considerably  in  moving  the  blood  on  toward  the 
heart.  It  is  worthy  of  remark  that  this  effect  is  more 
pronounced  at  the  time  the  muscles  need  the  most  active 
circulation ;  namely  when  they  are  in  action,  and  are  using 
the  most  blood.  The  heart  has  power  enough  to  pump 
the  blood  clear  around  from  each  ventricle  to  the  auricle 
of  the  other  side  of  the  heart ;  but  this  outside  aid  comes 
in  good  play  to  relieve  the  heart  at  a  time  when  it  has  an 
unusual  amount  of  work  to  do,  as  when  one  is  using  a 
large  number  of  muscles  vigorously. 

"  Every  active  muscle  is  a  throbbing  heart,  squeezing 
its  blood  tubes  empty  while  in  motion,  and  relaxing  so 
as  to  allow  them  to  fill  up  anew." 

Rate  of  Blood  Flow  in  the  Arteries,  Capillaries,  and 
Veins.  —  The  blood  flows  most  rapidly  in  the  arteries, 
slowest  in  the  capillaries.  Why  is  this  ? 

When  an  artery  divides,  the  two  branches  taken  together 
are  larger  than  the  one  artery  that  divided  to  form  them. 
Stated  more  exactly,  the  sum  of  the  areas  of  the  cross- 
sections  of  the  branches  is  greater  than  the  area  of  the 
cross-section  before  branching.  Hence  as  the  blood  flows 
on  it  is  continually  entering  wider  and  wider  channels ; 
and  we  are  told  that  the  united  cross-section  of  all  the 
capillaries  fed  by  the  aorta  is  several  hundred  times  that 
of  the  aorta  itself. 

The  Flow  of  the  Blood  compared  with  the  Current  of 
a  Stream.  —  If  we  walk  along  a  stream,  we  see  that  the 


6o 


PHYSIOLOGY. 


channel  varies  considerably  in  width  and  depth.  Where 
the  channel  is  large,  whether  from  increased  width  or  depth, 
there  the  current  is  slower,  but  wherever  the  channel  is 
reduced,  the  current  is  more  rapid.  So  the  stream  in 
the  relatively  narrow  artery  is  swift.  In  the  capillaries, 


Pulmonary  Vein     - 


Left  Auricle     .. 


Left  Ventricle 


Aorta 


Digestive  Tube 


Pulmonary  Artery 
Lymph  Vein 

Right  Auricle 

-  Right  Ventricle 
Caval  Vein 

-  Liver 


Fig.  28.    Plan  of  Circulation.    (Dorsal  View.) 

although  any  individual  channel  is  small,  these  channels 
all  together  are  wide ;  the  result  is  the  same  whether  a 
river  widens  out  into  a  single  lake,  or  divides  into  a  great 
number  of  channels  running  past  innumerable  islands. 


CIRCULATION  OF  THE  BLOOD.  6l 

All  the  tissues  of  the  body  may  be  regarded  as  so  many 
islands  lying  between  the  capillary  streams. 

The  Blood  Flow  in  the  Veins.  —  When  the  blood  re- 
collects in  the  veins  it  is  entering  narrower  channels,  and 
its  rate  is  quickened ;  but  as  the  veins  are  wider  than  the 
arteries,  the  stream  does  not  enter  the  heart  with  the  veloc- 
ity with  which  it  left  that  organ.  The  veins  hold  more 
blood  than  the  arteries,  and  in  dissecting  the  cat  or  rabbit 
it  will  be  noticed  that  the  arteries  are  emptied  of  blood; 
that  the  tissues  of  most  of  the  organs  are  fairly  free  from 
blood ;  but  -that  the  great  veins,  such  as  the  caval  veins, 
are  full. 

Blood  Tubes  compared  to  Two  Funnels.  —  If  the  blood 
tubes  leaving  the  heart  could  all  be  united,  they  would  be 
best  represented  by  a  funnel  with  its  tube  connected  with 
the  heart.  If  another  funnel  were  placed  with  its  mouth 
to  the  mouth  of  the  first,  their  point  of  union,  the  widest 
point,  would  represent  the  capillaries;  and  if  the  second 
funnel  had  a  wider  tube  than  the  first,  it  would  fairly  rep- 
resent the  veins  which  return  the  blood  to  the  heart. 

Nourishment  of  the  Walls  of  the  Heart  and  Blood 
Tubes. — The  cardiac  (coronary)  arteries  spring  from  the 
aorta  just  above  the  semilunar  valves,  and  send  blood  into 
the  muscular  walls  of  the  heart ;  and  these  arteries,  like 
others,  divide,  forming  capillaries,  through  which  the  heart 
muscle  is  nourished,  The  cardiac  veins  return  the  blood 
to  the  right  auricle. 

Influence  of  Gravity  on  Circulation.  —  Although  the 
heart  pumps  the  blood  around  through  the  body  inde- 
pendent of  the  force  of  gravity,  yet  the  circulation  is  influ- 
enced by  this  force.  For  instance,  a  person  who  has 


62  PHYSIOLOGY. 

fainted  should  be  laid  flat  on  his  back,  that  the  heart  may 
more  easily  drive  blood  to  the  brain.  Many  persons  go  to 
sleep  more  readily  while  sitting  than  while  lying  down. 
A  sore  hand  feels  less  pain  if  held  up,  as  in  a  sling,  than 
when  hanging  by  the  side,  and  a  sprained  ankle  does 
better  rested  on  a  chair,  as  less  blood  flows  to  it.  Nearly 
every  one  has  noted  the  pain  following  the  pressure  of 
blood  when  a  sore  hand,  or  foot,  is  suddenly  lowered. 

Experiments  illustrating  the  Effect  of  Gravity  on  Circulation.  — 
Let  all  the  pupils  in  the  class  stand.  Let  one  arm  hang  freely  by  the 
side.  Hold  the  other  arm  straight  up  as  far  as  the  clothing  will  readily 
permit.  Observe :  — 

1.  The  difference  in  the  color  of  the  two  hands. 

2.  The  difference  in  fullness,  both  in  the  feeling  of  fullness  and  in 
the  prominence  of  the  veins. 

3.  The  difference  in  temperature ;   place  the  backs  of  the  hands 
against  the  cheeks. 

The  position  largely  determines  the  amount  of  blood  in  the  hand, 
and  the  amount  of  blood  determines  the  temperature,  the  size,  and  the 
color.  

Summary. —  i.  The  heart  beats  about  seventy-two  times  a  minute. 

2.  The  pulse  is  a  wave  running  along  an  artery. 

3.  The  pulse  varies  with  age,  health,  food,  etc. 

4.  The  heart  has  two  main  cavities,  one  in  each  half  of  the  heart, 
and  two  independent  streams  are  flowing  through  it. 

5.  Valves  allow  the  blood  to  flow  through  the  heart  in  one  direc- 
tion, but  prevent  a  reversal  of  the  current. 

6.  The  heart  is  a  hollow  muscle,  and.  by  contraction  forces  the 
blood  out  into  the  arteries. 

7.  The  heart  works  rather  less  than  half  the  time. 

8.  The  large  arteries,  by  elastic  reaction,  push  the  blood  on  while 
the  heart  is  resting. 

9.  Circular  muscle  fibers  in  the  walls  of  the  medium-sized  arteries 
regulate  the  blood  supply  to  the  organs. 

10.  In  the  arteries  the  blood  flow  is  rapid  and  intermittent,  in  the 
capillaries  slow  and  constant. 


CIRCULATION"  OF  THE  BLOOD.  63 

11.  The  thin  walls  of  the  capillaries  allow  the  liquid  part  of  the 
blood  to  soak  out  and  nourish  the  tissues,  and  to  soak  back  into  the 
capillaries  bearing  waste  matter. 

12.  The  veins  are  thin  walled,  and  collapse  when  empty,  while  the 
arteries  are  thick  walled,  and  stand  open  when  empty  of  blood. 

13.  Arteries  carry  blood  from  the  heart,  while  veins  carry  it  toward 
the  heart. 

14.  The  veins  have  valves  which  allow  the  blood  to  pass  toward 
the  heart,  but  not  away  from  it. 

15.  Any  intermittent  pressure  on  the  veins  aids  the  blood  flow. 

1 6.  The  blood  flow  is  most  rapid  in  the  arteries,  slower  in  the  veins, 
slowest  in  the  capillaries. 

17.  Gravity  influences  circulation. 

Questions.  —  i.  Why  do  the  large  arteries  lie  deep? 

2.  In  which  direction  should  the  limbs  be  stroked  to  promote  circu- 
lation? 

3.  How  does  slapping  the  hands  around  the  body  warm  the  ringers? 

4.  How  can  a  horse  or  a  cow  be  comfortable  with  the  head  down 
for  a  long  time? 

5.  Why  are  the  walls  of  the  left  ventricle  thicker  than  those  of  the 
right  ? 


CHAPTER   V. 

CONTROL  OF  CIRCULATION.  —  THE   BLOOD  AND 
THE  LYMPH. 

The  Effect  of  the  Emotions  on  Circulation.  —  In  our 
every-day  experience  we  have  evidence  of  the  control  of 
the  heart  and  blood  tubes  by  the  nervous  system.  We  know 
that  certain  emotions  affect  the  circulation  of  the  blood ; 
for  instance,  blushing  and  pallor.  Certain  emotions  may 
also  quicken  or  retard  the  action  of  the  heart.  Excessive 
grief  or  joy  has  produced  sudden  death  by  stopping  the 
beat  of  the  heart. 

Let  us  look  a  little  more  closely  at  that  part  of  the 
nervous  system  that  has  such  intimate  relation  to  the 
blood  system. 

The  Rhythmic  Action  of  the  Heart. —  In  the  first 
place,  the  action  of  the  heart  is  automatic.  The  heart  of 
the  frog  continues  to  beat  a  long  time  after  it  is  removed 
from  the  body.  This  is  regarded  by  many  as  due  to  the 
action  of  certain  ganglia  imbedded  in  the  walls  of  the 
heart,  especially  in  the  auricles ;  while  others  say  that 
since  the  ventricle,  in  which  no  ganglia  have  been  found, 
may  beat  independently  of  the  auricles,  rhythmic  contrac- 
tion is  characteristic  of  heart  muscle,  and  that  we  are,  at 
present,  unable  to  explain  it. 

But  while  the  impulses  that  originate  the  action  of  the 
heart  arise  within  the  heart  itself,  still  the  beat  of  the  heart 
is  constantly  modified  by  nerve  impulses  reaching  it  from 
without. 

64 


Carotid  Plexus 


Superior  Cervical  Ganglion 


Middle  Cervical  Ganglion 


Pharyngeal  Branches 


Cardiac  Branches 


Deep  Cardiac  Plexus 


Superficial  Cardiac  Plexus 


Solar  Plexus 


Aortic  Plexus 


Lumbar  Ganglia 


Fig.  29.     Vertical  Section  of  Body,  showing  Sympathetic  Nerves  and  Ganglia  of  Right 
Sid,e  and  their  Connection  with  the  Cerebro-spinal  Nerves. 


66 


PHYSIOLOGY. 


Sympathetic  Nerve  Chains 
GRAY 


Sources  of  the  Heart's  Nerve  Supply.  — The  heart  re- 
ceives its  nerves  from  two  sources,  the  sympathetic  system 
and  the  vagus  (or  pneumogastric)  nerves. 

The  Sympathetic  Nervous  System.  — The  sympathetic 
nervous  system  consists  of  two  rows  of  ganglia  in  the  body 
cavity,  one  along  each  side 
of    the    spinal    column,    re- 
ceiving  branches  from  the 
spinal  nerves,  and  sending 
branches  to  all  the 
internal  organs  of 
the  body,  —  the 
heart  and  lungs  in   . 
the  thorax,  and  the 
stomach,  intestines,  and  the 
other  organs  of  the  abdomi- 


Ganglion  of 
Dorsal  Root 


Sympathetic 
Ganglion 


Fig.  30.    Relation  of  Spinal  Cord  and 
Sympathetic  Nervous  System  (Diagram). 


nal  cavity.  In  many  places 
these  nerves  form  a  thick 
network  called  a  plexus. 

One  very  large  plexus  is  on  the  dorsal  surface   of   the 

stomach,  and  is  called 
spinal  cord  the  solar  plexus. 


Sympathetic 
Ganglion 


The  Vagus  Nerves. 
—  The  vagus  nerves 
are  a  pair  of  the  cranial 
nerves  arising  from  the 
sides  of  the  spinal  bulb  ; 
and  passing  downward, 
they  give  branches  to 
the  pharynx,  the  gullet, 

the  stomach,  the  larynx,  the  windpipe,  the  lungs,  and  the 
heart.     Now,  whatever  other  function  the  vagus   nerves 


Fig-  31.    Ideal  Cross-section  of  the  Nervous 
System.    (After  Landois  and  Stirling.) 


CONTROL   OF  THE  CIRCULATION. 


67 


may  have,  they  seem  to  have  the  power  of  retarding,  or 
stopping  altogether,  the  beat  of  the  heart  ;  and  stimulation 
of  the  vagus  nerves  may  make  the  heart  pause  in  a  relaxed 
condition.  Other  nerves  may  quicken  the  heart  beat,  but 
the  vagi  are  regarded  as  a  break  on  the  heart's  action. 

Inhibition.  —  This  is  a  case  of  inhibition.  It  is  well 
known  that  a  severe  blow  over  the  stomach  may  cause  one 
to  faint  by  stopping  the  heart.  This 
is  due  to  reflex  inhibition  of  the  heart. 
The  blow  sends  a  nerve  impulse  by 
fibers  of  the  sympathetic  system  to 
the  center  in  the  spinal  bulb,  and 
thence  an  impulse  is  taken  by  the 
vagus  nerves  to  stop  the  heart. 

Vaso-constrictor  Nerves.  —  In  an 

experiment  with  the  rabbit's 
ear  it   has  been   shown  that 
stimulating    the    sympathetic 
nerve  in  the  neck  causes  the 
ear  to  become  pale.     This  is 
due  to  the  constriction  of  the 
arteries  of   the   ear,  because 
the    nerves    have    made    the 
muscle  fibers  of  these  arteries 
shorten.      Such    nerve  fibers 
are    called    constrictors,  or  vaso-con- 
strictors.      They  run    in   the   sympa- 
thetic  nerve,    but   have   their   origin 
and  center  in  the  spinal  bulb. 

Vaso-dilator  Nerves.  —  Other  fibers 

may  cause  the  opposite  effect,  namely,  dilation,  and  are 
therefore  called  vaso-dilators.     Examples  of  these  may  be 


Lungs  - 


Heart 


Stomach 


Fig.  32. 


Diagram  of  vagus 

Nerve. 


68  PHYSIOLOGY. 

found  running  to  the  arteries  of  the  limbs.  When  the 
muscles  of  any  organ,  say  the  legs,  act,  they  need  a  greater 
supply  of  blood.  Now,  at  the  same  time  that  nerve  im- 
pulses are  sent  to  the  muscles  of  the  legs  to  make  the 
muscles  shorten,  impulses  are  sent  along  other  fibers  of 
the  same  nerves  to  make  the  arteries  dilate,  and  allow 
more  blood  to  flow  to  these  muscles. 

Vaso-motor  Nerves.  —  The  vaso-constrictor  and  the 
vaso-dilator  nerves  taken  together  are  called  vaso-motor 
nerves. 

Centers  of  Control  of  Circulation.  —  The  centers  of 
control  of  the  blood  tubes  are  in  the  cerebro-spinal  nervous 
system.  There  is  no  evidence  that  the  sympathetic  gan- 
glia are  centers  of  reflex  action. 

Blushing.  —  How  is  it  that  the  face  sometimes  flushes 
so  suddenly  ?  Because  of  some  emotion,  you  say.  But 
how  does  the  emotion  bring  this  about  ?  We  have  already 
learned  about  the  muscles  in  the  wall  of  the  arteries.  We 
are  now  prepared  to  understand  that  in  the  normal  condi- 
tion nervous  impulses  are  acting  on  these  muscles,  keeping 
them  partly  shortened,  and  so  keeping  the  arteries  of  a 
moderate  size.  Under  the  influence  of  certain  emotions, 
the  caliber  of  the  arteries  is  suddenly  enlarged,  and  hence 
the  change  in  color. 

The  Regulation  of  the  Size  of  the  Arteries.  —  Through 
the  sympathetic  system  the  blood  supply  of  all  the  organs 
of  the  body  is  regulated.  Any  organ  needing  more  blood 
sends  a  message  (nerve  impulse)  to  some  nerve  center,  and 
in  response  nerve  impulses  are  sent  to  the  muscle  fibers  of 
the  supplying  artery,  and  the  amount  of  blood  sent  to  that 
organ  is  regulated.  For  instance,  a  piece  of  ice  is  laid 


CONTROL   OF  THE   C/RCULATfOJV. 


69 


upon  the  skin  of  the  hand.  The  part  becomes  pale,  as 
the  arteries  have  become  narrowed.  If  this  action  be  con- 
tinued, there  may  set  in  a  decided  reaction,  and  the  part 
become  more  red  than  usual,  when  the  reaction  has 
widened  the  artery  more  than  it  was 
before  the  constriction. 

Effect  of  Exercise  on  the  Size  of  the 
Arteries.  —  As  there  is  only  a  certain 
amount  of  blood  in  the  body,  it  is  evi- 
dent that  if  one  organ  receives 
an  extra  supply,  some  other  sympathetic 
organ  or  organs  must,  for  the  Ganglions 
time,  receive  less.  For  in- 
stance, one  begins  to  walk  vigorously. 
The  large  muscles  of  the  lower  limbs 
and  trunk  become  active,  and  they  need 
more  blood.  They  therefore  send  mes- 
sages to  some  nerve  center  (probably  in 
the  spinal  cord),  and  by  reflex  action  the 
arteries  supplying  the  lower  limbs  are 
widened,  and  these  muscles  receive  more 
blood.  But  these  muscles  make  up  a 
very  considerable  part  of  the  weight  and 
bulk  of  the  body.  While  in  action  they 
take  the  lion's  share  of  the  blood.  The 
brain,  at  such  a  time,  would  receive  less,  Fig.  33.  Ventral  Vie 
and  it  would  be  folly  to  expect  the  brain 
to  work  at  its  full  capacity  while  the 
blood  was  called  away  to  other  organs. 


of  Spinal  Cord  with 
Sympathetic  Gang- 
lions of  One  Side. 


Regulation  of  the  Effects  of  Exercise.  —  When  we  ex- 
ercise vigorously,  the  heart  beats  faster,  and  this  of  itself 
would  tend  to  increase  the  blood  supply  to  all  organs. 


70  PHYSIOLOGY. 

But  this  mechanism  for  widening  the  channel  leading  to 
the  working  organs,  while  the  arteries  to  the  other  organs 
are  made  smaller,  or  at  least  are  not  enlarged,  solves  the 
problem  of  supplying  each  part  according  to  a  greatly 
varying  need,  while  not  sending  too  much  to  a  part  not 
needing  it. 

EFFECTS  OF  ALCOHOL  ON   THE   CIRCULATION. 

"  Alcohol  stimulates  the  heart,  producing  increased  force 
and  rapidity  of  the  cardiac  beat.  It  thus  tends  to  increase 
the  blood  pressure  by  acting  on  the  heart,  and  to  increase 
the  flow  of  blood  from  the  arteries  into  the  veins.  The 
effect  on  the  blood  pressure  is,  however,  partly  counter- 
acted by  a  coincident  dilatation  of  the  blood  vessels  of  the 
skin,  which  thus  become  flushed,  and  tends  to  produce 
more  sensible  perspiration." — Treatise  on  Hygiene,  STE- 
VENSON and  MURPHY. 

"The  warm  and  flushed  condition  of  the  skin  which 
follows  the  drinking  of  alcoholic  fluids  is  probably,  in  a 
similar  manner,  the  result  of  an  inhibition  of  that  part 
of  the  vaso-motor  center  which  governs  the  cutaneous 
arteries."  •  —  FOSTER. 

The  control  of  the  muscles  in  the  walls  of  the  arteries 
being  thus  interfered  with,  the  circular  muscles  are  no 
longer  made  to  shorten,  and  the  artery  dilates,  thus  allow- 
ing more  blood  to  flow  into  it. 

We  may  thus  account  for  the  flushing  of  the  skin  of  the 
face,  which  in  many  individuals  quickly  betrays  indulgence 
in  alcoholic  drink.  If  this  flushing  is  too  often  repeated, 
the  arteries  gradually  "lose  tone,"  and  the  condition  be- 
comes permanent.  The  circulation  in  the  whites  of  the 
eyes  may  be  affected,  making  them  "bloodshot." 


CONTROL    OF  THE  CIRCULATION.  ?1 

Similar  congestion  occurs  in  the  mucous  membrane  of 
the  stomach  from  the  presence  of  alcohol,  which  may 
become  a  permanent  inflammation  followed  in  time  by 
very  extensive  changes  in  appearance  and  function.  It 
is  said  that  most  of  the  alcohol  swallowed  is  absorbed 
directly  from  the  stomach,  and  hence  the  intestines  are 
not  so  directly  affected. 

Good  authorities  state  that  alcohol  arrests  the  develop- 
ment of  the  corpuscles.  It  diminishes  the  size,  alters  the 
form,  and  reduces  the  number  of  the  corpuscles.  Since 
the  work  of  the  blood  corpuscles  is  so  important  this 
reduction  in  their  number  and  efficiency  must  very 
appreciably  affect  the  nutrition  of  the  body  as  a  whole. 
When  the  blood  is  "  out  of  order"  the  body  is  out  of  order. 

The  Blood, — The  blood  is  composed  of  a  clear  liquid, 
the  plasma,  and  the  blood  cells,  or  corpuscles.  In  a  drop 
of  blood  under  the  microscope  the  plasma  occupies  the 
clear  spaces  between  the  corpuscles.  The  corpuscles 
make  up  one  third  of  the  bulk  of  the  blood,  and  the 
plasma  two  thirds. 

Microscopic  Examination  of  the  Blood.  —  To  get  a  drop  of  blood 
from  the  finger,  wind  a  cord  around  the  finger,  beginning  at  the  base, 
drawing  the  cord  moderately  tight,  until  the  last  joint  is  reached.  By 
this  time  the  end  of  the  finger  is  usually  well  distended  with  blood. 
With  a  clean  needle  make  a  quick,  sharp,  light  puncture  near  the  base 
of  the  nail ;  this  ordinarily  brings  a  small  amount  of  blood.  Put  a 
small  drop  on  each  of  several  slides  and  quickly  cover  with  coverslips. 
Examine  with  a  high  power. 

The  Colored  Corpuscles.  —  These  are  often  called  the 
red  corpuscles.  But  while  in  the  mass  they  give  the 
blood  a  red  appearance,  individually  they  are  faint  yellow- 
ish red.  In  shape  they  are  seen  to  be  circular  disks,  hol- 
lowed on  each  side  like  a  sunken  biscuit.  As  they  are 


72  PHYSIOLOGY. 

hollowed  on  both  sides  they  are  more  accurately  described 
as  biconcave.  These  corpuscles  tend  to  gather  side  by 
side,  in  rolls,  like  coins.  They  are  cells  without  nuclei. 

The  Colorless  Corpuscles.  —  In  the  open  spaces  be- 
tween the  rolls  of  colored  corpuscles  may  occasionally 
be  found  some  spherical  corpuscles.  They  are  usually 


White  Corpuscles 


HIGHLY    MAGNIFIED 


White  Corpuscle 


Red  Corpuscles 
in  Rolls 


MODERATELY    MAGNIFIED 
Fig.  34.     Red  and  White  Corpuscles  of  the  Blood. 

called  the  white  corpuscles,  but  are  better  designated  as 
the  colorless  corpuscles,  since  the  others  have  only  a  slight 
color,  and  these  have  none.  They  usually  have  a  dotted 
appearance.  It  is  not  so  easy  to  distinguish  the  two  kinds 
of  corpuscles  as  it  is  in  the  case  of  the  frog's  blood,  for  the 
two  kinds  are  more  nearly  of  the  same  size  in  the  human 


CONTROL   OF  THE   CIRCULATION.  73 

blood  ;  and,  further,  when  the  colored  corpuscles  of  human 
blood  are  seen  flatwise  they  present  a  circular  outline,  while 
the  frog's  colored  corpuscles  are  elliptical.  But  with  a 
little  study  the  two  may  be  distinguished.  As  in  the  frog's 
blood,  the  colorless  corpuscles  have  ameboid  movements, 
though  they  are  not  very  marked  unless  the  blood  be 
warmed  to  about  the  temperature  of  the  human  body. 

Flexibility  and  Elasticity  of  the  Corpuscles.  —  It  will 
be  well  here  to  examine  again  the  frog's  web.  (See  p.  54.) 
It  will  occasionally  be  seen  that  when  one  of  the  colored 
corpuscles  is  pressed  against  an  angle  at  the  forking  of 
the  blood  stream,  it  is  sometimes  bent,  and  that  as  soon  as 
the  pressure  is  discontinued  the  corpuscle  springs  back  to 
its  former  shape,  showing  that  it  is  elastic. 

Frog's  Blood.  —  A  drop  of  frog's  blood,  mounted  as  the  human  blood 
was,  will  be  helpful,  as  there  is  a  very  decided  difference  in  the  size  and 
shape  of  the  colored  and  colorless  corpuscles.  Further,  the  colorless 
corpuscles  of  the  frog  will  show  ameboid  movements,  i.e.  slow  changes 
of  form,  if  watched  a  while. 

The  Plasma.  —  The  plasma  consists  chiefly  of  water, 
having  in  solution  various  salts,  including  common  salt; 
it  also  contains  the  nourishing  materials  for  the  tissues. 
These  nourishing  materials,  obtained  from  the  food  by 
digestion,  consist  chiefly  of  proteids,  fats,  and  sugar.  The 
plasma  also  contains  waste  matters,  from  the  working 
tissues,  on  their  way  out  of  the  body.  How  the  food  is  pre- 
pared for  the  building  of  tissue,  and  how  the  waste  matter 
is  removed  from  the  body,  we  shall  study  a  little  later. 

The  Color  of  Blood.  — The  difference  in  color  of  an  in- 
dividual corpuscle  and  the  blood  in  the  mass  may  be  better 
understood  by  comparing  it  with  something  that  we  see 
more  frequently.  A  tumbler  of  currant  jelly  has  a  rich, 


74  PHYSIOLOGY. 

red  color,  but  a  thin  layer  of  the  same  jelly,  as  when  one 
takes  a  spoonful  on  a  plate,  has  a  pale  color,  more  yellow- 
ish. The  colorless  plasma  with  the  colored  bodies  in  it 
may  be  compared  to  a  glass  dish  filled  with  cranberries 
and  water. 

Hemoglobin.  —  The  coloring  matter  in  the  blood,  then, 
is  wholly  in  the  colored  corpuscles.  Examination  of  these 
corpuscles  shows  that  their  color  is  due  to  a  substance 
called  hemoglobin.  There  is  a  small  amount  of  iron  in 
the  hemoglobin,  and  the  presence  of  this  small  quantity 
of  iron  appears  to  be  essential  to  give  the  blood  its  color. 
When  we  come  to  the  study  of  respiration  we  shall  see 
that  the  hemoglobin  in  the  corpuscles  is  the  chief  agent  in 
picking  up  the  oxygen  from  the  air  in  the  lungs  and  carry- 
ing it  to  the  tissues  in  the  body. 

The  Coagulation  of  Blood.  —  When  the  blood  escapes 
from  its  natural  channels  it  usually  changes  from  a  liquid 
to  a  jelly-like  condition.  This  is  known  as  coagulation. 
It  is  due  to  the  formation  of  threads  of  fibrin  from  the 
plasma.  These  threads  of  fibrin  entangle  and  inclose  the 
corpuscles,  and  the  two  constitute  the  clot,  or  coagulum,  as 
it  is  more  technically  termed.  The  liquid  that  afterward 
separates  from  the  clot  is  the  serum,  and  differs  from  the 
plasma  only  in  the  removal  of  the  fibrin,  which  is  exceed- 
ingly small  in  quantity,  though  of  great  importance  in  its 
action.  Many  experiments  have  been  made,  and  much 
has  been  written  about  the  coagulation  of  the  blood,  and 
perhaps  its  real  cause  is  not  yet  clear.  But  we  know  that 
the  coagulation  often  serves  to  stop  the  flow  of  blood  from 
wounds,  and  this  is  its  main  use. 

Fibrin.  —  If  freshly  drawn  blood  be  stirred  rapidly  with 
a  bundle  of  wires  (perhaps  the  most  convenient  stirrer  is 


CONTROL   OF  THE   CIRCULATION.  ?$ 

a  little  roll  of  wire  screen),  there  will  soon  collect  on  the 
wires  a  stringy  substance.  Thorough  washing  will  soon 
leave  this  colorless.  It  is  fibrin.  If  the  stirring  has  been 
done  thoroughly,  the  blood  will  no  longer  clot,  no  matter 
how  long  it  may  stand. 

Liquid  Blood  and  Coagulated  Blood.  —  The  following 
scheme  shows  the  difference  between  the  liquid  blood  and 
the  coagulated  blood  :  — 

(  Serum 


Liquid  Blood 


Plasma. 


(  Fibrin 


Clot 


Coagulated  Blood. 


Corpuscles 

Amount  of  Blood. — The  blood  constitutes  about  one 
thirteenth  of  the  weight  of  the  body.  In  a  body  weighing 
one  hundred  and  fifty  pounds  this  would  be  about  six 
quarts. 

Chemical  Reaction  of  Blood.  —  Blood  is  alkaline. 

Specific  Gravity  of  Blood.  —  Blood  is  somewhat  heavier 
than  water,  owing  to  the  salts  and  other  matters  dissolved 
in  it. 

Quantity  of  Blood  in  Different  Organs  (approximately). 
—  i.  One  fourth  is  in  the  heart  and  the  larger  arteries 
and  veins  (including  those  of  the  lungs). 

2.  One  fourth  in  the  liver. 

3.  One  fourth  in  the  skeletal  muscles. 

4.  One  fourth  in  the  other  organs. 

The  Lymph  Spaces. — We  have  seen  that  the  capillaries 
have  very  thin  walls.  Through  their  walls  part  of  the 
plasma  of  the  blood  soaks  out,  and  is  then  called  lymph. 
It  passes  into  irregular  cavities  in  the  tissue  called  lymph 
spaces.  Most  of  these  lymph  spaces  are  minute  chinks  or 


76  PHYSIOLOGY. 

crevices  in  the  connective  tissues  of  the  different  parts  of 
the  body. 

The  Lymph  Tubes.  —  Opening  out  of  the  lymph  spaces 
are  irregular  passage  ways  called  lymph  capillaries,  and 
these  lymph  capillaries  are  continuous  with  thin-walled 
tubes,  the  lymph  tubes.  These  lymph  tubes  might  be 
called  the  lymph  veins,  since  they  join  still  larger  tubes, 
closely  set  with  valves,  similar  to  those  of  the  veins.  But, 
unlike  the  blood  veins,  the  lymph  veins  do  not  gradually 
increase  in  size  by  confluence.  They  suddenly  form  a 
large  tube,  the  receptacle  of  the  chyle,  beginning  in  the 
upper  part  of  the  abdomen.  This  tube  soon  narrows  and 
passes  through  the  diaphragm,  close  to  the  spinal  column, 
and  up  along  the  column  near  the  aorta,  and  empties  into 
the  veins  of  the  neck  at  the  junction  of  the  left  jugular 
and  left  subclavian  veins.  This  tube  is  the  thoracic  duct, 
or  the  main  lymph  duct.  It  has  numerous  valves,  and, 
like  some  of  the  smaller  lymph  veins,  it  presents  a  beaded 
appearance,  due  to  the  filling  and  bulging  out  of  the  valves. 
In  the  right  side  of  the  neck  is  a  short  right  lymph  duct 
which  receives  lymph  from  the  right  side  of  the  head, 
neck,  and  thorax,  and  from  the  right  arm.  The  lymph 
tubes,  as  a  whole,  are  usually  called  the  "lymphatics." 

Lymph  Spaces  in  the  Frog.  —  In  dissecting  the  frog,  the  looseness 
of  the  skin  is  very  noticeable.  The  large  spaces  under  the  skin  are 
lymph  spaces.  Sometimes  considerable  lymph  is  found  here,  so  that 
in  holding  up  a  frog  the  sagging  of  the  skin  from  the  weight  of  the 
lymph  may  be  easily  seen. 

Valves  at  the  Mouth  of  the  Lymph  Tubes.  —  There 
are  valves  where  these  lymph  ducts  empty  into  the  veins 
which  prevent  any  reflow  of  liquid  into  the  ducts,  but  allow 
the  lymph  to  pass  freely  into  the  veins. 


CONTROL    OF  THE   CIRCULATION.  77 

Muscle  Fibers  in  the  Walls  of  the  Lymph  Tubes.  - 

There  are  plain  muscle  fibers  in  the  walls  of  the  lymph 
ducts. 

Lymphatic  Glands.  —  In  its  course  the  lymph  passes 
through  many  kernel-like  masses,  the  lymphatic  glands. 
Lymph  contains  corpuscles  which  are  considered  identical 
with  the  colorless  blood  corpuscles.  It  is  tho'ught  that 
these  corpuscles  are  formed  in  the  lymphatic  glands. 

The  Flow  of  Lymph. — The  flow  of  lymph  is  partly 
due  to  the  blood  pressure  in  the  capillaries ;  this  pressure 
is  caused  by  the  heart.  (In  the  frog  there  are  two  small 
hearts,  —  not,  however,  near  the  blood-pumping  heart,— 
and  these  pump  the  lymph  along.)  In  our  bodies  the  flow 
of  lymph  is  largely  aided  by  any  pressure  that  may  be 
brought  to  bear  on  the  lymph  veins ;  for,  on  account  of 
the  valves,  as  in  the  blood  veins,  any  pressure  must  push 
the  liquid  toward  the  heart.  Thus  the  action  of  the  mus- 
cles in  the  limbs,  in  the  chest,  in  the  abdomen,  in  the 
movements  of  breathing,  and  in  the  bending  of  the  body, 
etc.,  all  help  in  this  flow,  which  is  always,  probably,  very 
much  slower  than  that  in  the  blood  veins. 

Relations  of  Blood  Flow  and  Lymph  Flow.  —  It  will 
now  be  seen  that  while  the  blood  leaves  the  left  ventricle 
by  one  tube,  the  aorta,  it  returns  to  the  right  auricle,  not 
merely  by  the  two  caval  veins,  but  that  a  part  of  the  blood 
(i.e.  of  the  liquid  part  of  it)  does  not  return  by  blood  veins, 
but  having  left  the  blood  system  proper  through  the  thin 
walls  of  the  capillaries,  it  is  brought  back  to  the  heart  by 
the  lymph  veins,  which,  however,  join  the  blood  veins  just 
before  they  empty  into  the  heart.  There  is,  in  other 
words,  only  one  set  of  distributing  tubes,  but  there  are  two 
sets  of  collecting  or  returning  tubes. 


PHYSIOLOGY. 


Left  Jugular  Vein 

Mouth  of  Lymph  ... 
Vein 


Right  Lymph  Vein 

Right  Subclavian 
Vein 


Precaval  Vein 


Postcaval  Vein 


Main  Lymph  Vein 
(Thoracic  Duct) 


Lymph  Capillaries 


Blood  Capillaries 


Fig.  35.   Diagram  of  the  Circulation  of  Blood  and  Lymph  (Dorsal  View). 


CONTROL   OF  THE  CIRCULATION. 


79 


Lymph 


Capillary 


The  Lymph.  —  Lymph  is  a  clear  liquid.  (Chyle  and 
the  lacteals  will  be  considered  when  we  study  digestion.) 
It  is  more  watery  than  the  blood  plasma,  but  contains  a 
share  of  all  its  nutritious  substances.  Lymph  may  be 
defined  as  "diluted  blood  minus  red  corpuscles."  The 
blood  proper  never  reaches  the  tissues. 

The  Cells  of  the  Body  live  in  Lymph. —  The  cells 
of  the  tissues  are  bathed  in  the  lymph  which  fills  the 
spaces  in  the  connective 
tissue  (and  we  have  seen 
that  the  connective  tissue 
pervades  nearly  all  the  tis- 
sues of  the  body),  as  water 
may  fill  the  spaces  left 
between  stones  built  into 
a  wall.  The  cells  get  all 
their  nourishment  from  the 
lymph,  and  into  the  lymph 
they  throw  all  their  waste 
matter.  Each  cell  may  be 
compared  to  an  individual 
ameba,  which  lives  in 
water,  and  takes  all  its 
nourishment  from  that 
water,  and  throws  all  its 
waste  product  into  the 
same  water.  As  water  is 
the  medium  in  which  the 

ameba   lives,  so   we   may  say   lymph   is   the   medium   in 
which  the  cells  of  the  body  live. 

Cells  of  the  Body  Aquatic.  —  The  cells  of  the  body, 
i.e.  all  the  active,  working  cells,  may,  therefore,  be  said 


Oxygen 


Food      


Water 


Other 
Wastes 


Fig.  36.     Relation  of  Blood  and  Muscle. 
(Lymph  being  Middleman.) 


80  PHYSIOLOGY, 

to  live  an  aquatic  life,  and  only  dead  cells,  as  of  hair, 
epidermis,  etc.,  live  in  air.  We  might  also  say  that  not 
only  the  human  body,  but  all  animal  life  is  aquatic. 

Importance  of  Lymph.  —  We  can  see  that  the  move- 
ment and  renewal  of  lymph  are  as  necessary  as  the  circu- 
lation of  the  blood  itself ;  is,  in  fact,  the  most  important 
part  of  it. 

Lymph  Cavities  or  Serous  Cavities.  — We  have  noticed 
the  pericardial  liquid.  There  is  also  a  small  quantity  of 
similar  liquid  around  the  lungs  in  the  pleural  cavities,  and 
in  the  abdominal  or  peritoneal  cavity,  around  the  digestive 
organs ;  also  in  the  cavities  of  the  brain.  The  liquid  in 
each  case  is  lymph,  and  these  cavities,  often  called  serous 
cavities,  are  lymph  cavities.  They  communicate  with  the 
lymph  tubes. 

Dropsy.  —  In  health  the  amount  of  the  liquid  in  these 
cavities  is  small,  but  in  certain  disorders  it  may  accumu- 
late. In  general,  such  affections  are  called  "dropsy." 
The  lymph  may  also  accumulate  in  the  tissues  of  the 
extremities,  causing  swelling  of  the  limbs. 

Variation  in  the  Composition  of  Lymph.  —  It  is  evi- 
dent that  the  materials  needed  by  the  cells  of  the  different 
tissues  are  not  the  same.  So,  as  one  tissue  takes  certain 
materials  and  another  tissue  others,  it  is  clear  that  the 
lymph  will  not  be  of  quite  the  same  composition  in  the 
different  parts  of  the  body.  This  difference  is  further 
due  to  the  difference  in  the  waste  products  thrown  out 
by  the  different  cells.  Hence  the  composition  of  the 
blood  varies  considerably  in  different  regions.  But  the 
lymph  from  all  the  tissues  unites  with  the  blood  from  all 
the  tissues  in  the  right  heart,  and  on  their  way  to  it  in  the 


CONTROL   OF  THE  CIRCULATION.  8 1 

larger  veins.  So  the  constant  slight  differences  in  com- 
position of  the  blood  and  lymph  in  the  various  tissues  are 
counterbalanced  by  the  mingling  of  the  currents  from 
these  various  parts  in  the  large  arteries  and  veins. 

The  Spleen.  —  The  function,  or  functions,  of  the  spleen  are  not  well 
understood.  It  is  believed  to  have  something  to  do  with  the  renova- 
tion of  the  blood,  perhaps  forming  colorless  corpuscles  and  destroying 
colored  corpuscles.  At  any  rate,  the  physiologists  generally  call  it  a 
blood  gland.  It  is  unlike  true  glands  in  that  it  has  no  duct,  and  forms 
no  secretion  to  be  poured  into  any  cavity,  like  the  glands  of  excretion 
and  secretion.  It  has  been  found,  in  the  case  of  accidents  to  man,  and 
by  experiment  on  the  lower  animals,  that  life  may  continue  after  this 
organ  has  been  removed. 

Massage.  —  A  system  of  pressing,  rubbing,  and  knead- 
ing the  muscles  is  known  as  massage.  It  helps  the  flow 
of  the  blood  and  lymph,  thus  aiding  in  washing  out  the 
waste  products  from  the  muscles  and  other  parts  of  the 
body  that  are  to  be  reached  by  pressure.  We  have  seen 
that  one  of  the  benefits  of  exercise  is  to  promote  the  cir- 
culation of  the  blood  and  of  the  lymph,  and  so  to  help 
get  rid  of  the  waste  matters  that  are  produced  by  the 
activity  of  the  various  organs.  Many  invalids  cannot  take 
active  exercise.  So  this  passive  exercise  may  very  fairly 
take  its  place,  and  assist  in  the  nutrition  of  the  tissue  by 
accelerating  the  flow  of  blood  and  lymph,  bringing  new 
nourishment  and  carrying  away  wastes.  For  students 
who  do  not  take  sufficient  exercise  it  is  a  good  thing  to 
rub  the  body  thoroughly  and  briskly,  not  only  after  a 
bath,  but  often  with  the  hands  or  with  a  dry  towel. 

Transfusion  of  Blood.  —  Transfusion  of  blood  is  the  transfer  of 
blood  from  the  blood  vessels  of  one  animal  to  those  of  another.  Trans- 
fusion may  be  direct  or  immediate,  as  when  the  blood  vessels  of  the 
two  animals  are  connected  by  tubing  so  that  the  blood  passes  from  one 
to  the  other  without  exposure  to  the  air ;  in  indirect  or  mediate  trans- 


82  PHYSIOLOGY. 

fusion  the  blood  is  first  drawn  into  a  receptacle.  In  indirect  transfusion 
the  blood  is  often  defibrinated  before  transference.  The  blood  may  be 
introduced  either  into  an  artery  or  a  vein;  if -into  a  vein  it  is  sent  in 
the  direction  of  the  natural  flow,  i.e.  toward  the  heart ;  if  into  an  artery, 
in  either  direction.  Soon  after  the  discovery  of  the  circulation  of  the 
blood  the  operation  of  transfusion  began  to  be  practiced,  and  high 
hopes  were  indulged  in  as  to  its  value.  But  it  was  soon  found  to  be 
attended  by  so  much  danger  that  it  is  now  seldom  used.  It  is  resorted 
to  (i)  after  great  loss  of  blood,  (2)  after  some  forms  of  poisoning  part 
of  the  blood  is  withdrawn  and  replaced  by  fresh  blood,  and  (3)  in 
certain  disordered  conditions  of  the  blood.  The  chief  dangers  are  (i) 
the  introduction  of  air  which  forms  minute  bubbles  and  stops  the  blood- 
flow  in  the  capillaries,  (2)  the  introduction  sometimes  causes  coagula- 
tion within  the  blood  vessels,  and  (3)  the  serum  of  the  introduced 
blood  sometimes  destroys  the  corpuscles  of  the  blood  to  which  it  is 
added.  In  the  earlier  practice  lamb's  blood  was  employed,  but  now 
when  transfusion  is  practiced  on  man  only  human  blood  is  used.  It 
has  been  found  safer  and  better  after  great  loss  of  blood  from  hemor- 
rhage, to  introduce  a  salt  solution  of  about  the  natural  degree  of  salt- 
ness  of  the  blood  ;  this  restores  the  normal  volume  of  circulating  liquid, 
and  avoids  most  of  the  dangers  except  that  of  introducing  air.  The 
numerous  fatal  results  of  this  operation  have  shown  that  it  should  not 
be  resorted  to  except  in  cases  of  extreme  necessity. 

For  directions  about  stopping  the  flow  of  blood  from 
wounds  see  Chapter  XXIII.  and  the  books  named  below. 

READING.  —  Prompt  Aid  to  the  Injured,  Doty ;  Emer- 
gencies, Dulles;  Emergencies,  Howe;  First  Aid  to  the 
Injured,  Lawless;  First  Aid  to  the  Injured,  Morton;  First 
Aid  in  Illness  and  Injury,  Pilcher ;  Sickness  and  Accidents, 
Curran. 

What  other  process  keeps  pace  with  the  coursing  of  the 
blood  through  the  body,  being  its  running  mate,  so  to 
speak  ?  

Summary.  —  i .  Blushing,  and  other  variations  in  blood  supply,  are 
under  the  control  of  the  sympathetic  nervous  system. 

2.   The  sympathetic  nervous  system  consists  of  two  rows  of  ganglia 


CONTROL   OF  THE  CIRCULATION".  83 

in  the  body  cavity  near  the  spinal  column,  with  fibers  running  to  the 
internal  organs.  It  is  also  connected  with  the  cerebro-spinal  nervous 
system. 

3.  The  heart  beat  is  automatic  and  rhythmic. 

4.  The  heart  beat  is  regulated  by  the  sympathetic  nervous  system 
and  by  the  vagus  nerves. 

5.  The  blood  consists  of  a  liquid,  the  plasma,  in  which   float  the 
colored  and  colorless  corpuscles. 

6.  When  blood  is  shed  it  coagulates,  tending  to  check  its  own 
escape. 

7.  Lymph  is  like  the  blood  diluted  and  lacking  the  colored  cor- 
puscles. 

8.  A  set  of  lymph  tubes  conveys  the  lymph  into  the  veins  to  join 
the  flow  toward  the  heart. 

9.  In  its  course  the  lymph  passes  through  the  lymphatic  glands. 

Questions.  —  i.   What  makes  the  hands  grow  red  and  puff  up  on 
sitting  in  a  warm  room  after  snow  balling? 

2.  How  is  a  mustard  plaster  effective? 

3.  Why  does  light  exercise  before  retiring  promote  sleep? 

4.  Why  are  the  feet  often  cold  after  studying? 

5.  How  does  the  application  of  ice,  or  cold  water,  relieve  head- 
ache? 

6.  Why  should  the  clothing  be  changed  after  getting  wet? 

7.  What   is   the    meaning  of   humor,    in    the   expressions  "good- 
humored,"  "  bad-humored "  ?     Have  these  expressions  a  real  physio- 
logical significance? 


CHAPTER  VI. 


RESPIRATION. 

The  Close  Relation  between  Circulation  and  Respira- 
tion. —  Is  it  not  a  very  striking  fact  that  we  take  one 
breath  for  every  four  heart  beats  ?  That  whatever  quick- 
ens the  breathing  also  quickens  the  heart,  so  that  the  two 

always  keep  in  al- 
most the  same  ratio  ? 
Let  us  learn  what 
are  the  many  inti- 
mate relations  of 
the  blood  pump  and 
the  air  pump,  the 
blood  system  and 
the  air  system,  of 
Circulation  and  Res- 
piration. 

The    Organs    of 
Respiration.— 

1 .  The  lungs  and 
air  tubes. 

2.  The  structures 
which  increase  and  diminish  the  size  of  the  chest,  princi- 
pally the  diaphragm,  and  the  muscles  acting  on  the  ribs. 

The  Parts  of  the  Lungs.  —  i.   The  Air  Vesicles,  an 

immense  number  of  small  sacs,  which  communicate  with 

84 


Fig.  37.   The  Trachea  and  Bronchial  Tubes,  showing 
Two  Clusters  (Alveoli))  of  Air  Vesicles. 


RESPIRATION. 


1.  Pulmonary  Orifice 

2.  Aortic  Orifice 


3.  Left  Auriculo-Ventricular  Orifice 

4.  Right  Auriculo-Ventricular  Orifice 


The  heavy  black  line  between  the  heart  and  the  liver  represents  the  diaphragm. 

Fig.  38.    Front  View  of  the  Thorax.    The  Ribs  and  Sternum  are  represented  in 

Relation  to  the  Lungs,  Heart,  and  other  Internal  Organs. 


86 


PHYSIOLOGY. 


the  outer  air  by  the  bronchial  twigs,  the  bronchi,  and  the 
trachea. 

2.  The  Pulmonary  Capillaries,  forming  a  thick  network 
around  and  between  the  air  sacs.  These  capillaries  receive 
their  blood  from  the  pulmonary  artery,  and  return  it  to  the 
heart  by  the  pulmonary  veins. 

Elastic  Tissue  in  the  Lungs. — The  air  vesicles,  with 
their  supplying  air  tubes  and  their  surrounding  blood  tubes, 
are  bound  together  by  elastic  tissue,  which  fills  up  most  of 
the  intervening  space. 

The  Windpipe  or  Trachea. — The  windpipe  has  in  its 
walls  C-shaped  cartilages,  with  the  open  part  of  the  C 
on  the  dorsal  surface.  These  cartilages  continue  in  the 
bronchi,  and  so  on  until  in  the  smaller  twigs  they  finally 
disappear.  The  cartilages  are  held  together,  and  the 
dorsal  gap  of  the  cartilages  (the  gap  would  be  like  that  of 
a  series  of  horseshoes  piled  one  on  top  of  another)  bridged, 
by  tough  fibrous  tissue,  with  much  elastic  tissue,  and 
with  plain  muscle  fibers ;  the  plain  muscle  fibers  are  very 
abundant  in  the  smaller  air  tubes. 

The   Mucous   Membrane.  —  The  lining  of  the  trachea 

is  a  mucous  mem- 
brane. It  pours 
out  on  its  surface 
a  substance  some- 
what like  white  of 
egg,  called  mucus. 
This  keeps  the  air 

Fig.  39.     Ciliated  Cells  lining  the  Air  Tubes  (x  300). 


particles  of  dust  that  are  in  the  inspired  air.  There  is  a 
constant  slow  current  of  mucus  toward  the  throat,  whence 
it  is,  from  time  to  time,  hawked  up. 


RESI'IRATION. 


Cilia.  —  This  current  of  mucus  is  caused  by  the  cilia 
projecting  from  the  lining  cells  of  the  trachea.  They  are 
little  hairlike  projections,  in  countless  numbers,  like  a  field 
of  grass,  each  stalk  having  the  power  of  bending  back  and 
forth,  making  a  quick  stroke  toward  the  throat,  then  a 
slower  recover  stroke.  Thus  the  united  wavelike  action 
of  the  myriads  of  lashing  cilia  paddles  the  mucus  head- 
ward.  It  is  a  very  common  error  to  suppose  that  the  cilia 
produce  air  currents.  This  is  not  their  function,  and  it 
can  readily  be  seen  that  they  cannot  create  currents  of  air, 
as  they  are  wholly  submerged,  like  grass  growing  on  the 
bottom  of  a  shallow  pond  of  slimy  water. 

Location  of  Mucous  Membrane.  —  All  the  cavities  and 
passages  in  the  body  to  which  the  air  has  access,  such  as 
the  digestive  and  respiratory  passages,  etc.,  are  lined  by 
mucous  membrane  (not  all 

Ciliated).  Trachea 

The  Pleura.— The  out- 
side of  each 
lung  is  cov- 
ered by  a  thin 
adherent  mem- 
brane, the  pleu- 
ra, which  com- 
pletely invests 
it,  except  at  the  root  of 
the  lung,  where  the  bron- 
chus and  blood  tubes 
enter.  Here  the  pleura 
turns  toward  and  adheres  to  the  inner  wall  of  the  chest, 
forming  its  lining  (still  called  the  pleura),  and  below  passes 
over  the  anterior  surface  of  the  diaphragm.  The  lung  is 


Pleural  Space 
(Exaggerated) 


Chest  Wall-  -• 


~~~  Pleura 


Fig.  40.     Diagram  of  the  Lungs  and  Pleurae. 


88  PHYSIOLOGY. 

thus  free,  except  at  its  root,  where  the  air  and  blood  tubes 
enter.  A  very  small  quantity  of  liquid  moistens  the  con- 
tiguous surfaces  of  the  pleurae  on  the  outside  of  the  lung 
and  the  inside  of  the  chest  wall,  so  they  move  easily  one 
upon  the  other  during  respiration.  As  the  lungs  are 
always  distended  enough  to  fill  the  chest  cavity,  these  two 
surfaces  are  always  in  contact.  In  pleurisy  (inflammation 
of  the  pleurae)  pain  is  felt  in  breathing  from  friction  or 
adhesion  of  these  surfaces. 

Important  Facts  concerning  Respiration.  —  In  study- 
ing respiration,  let  us  constantly  keep  in  mind  these 
facts : — 

1.  The  lungs  are  highly  elastic,  and 

2.  Highly  porous,  each  air  vesicle  being  in  direct  com- 
munication with  the  outer  air  by  means  of 

3.  Air  tubes  that  always  stand  open 

4.  And  are  always  moist  internally. 

5.  The  pulmonary  capillaries  closely  invest  each  air 
vesicle. 

6.  The  lungs  are  always  expanded  enough  to  fill  all 
the  space  in  the  chest  not  occupied  by  other  organs,  and 

7.  Freely  movable,  except  at  the  place  of  entrance  of 
the  bronchi  and  blood  tubes. 

8.  The  smooth,  moist  pleurae. 

The  Diaphragm.  —  The  diaphragm  is  a  thin  muscle 
making  a  complete  partition  between  the  abdominal  cavity 
and  the  chest  cavity.  It  is  convex  anteriorly,  concave  pos- 
teriorly ;  its  ventral  border  is  attached  to  the  inside  of  the 
chest  wall  about  opposite  the  lower  end  of  the  breast  bone, 
thence  obliquely  along  the  border  of  the  ribs  (as  felt  in 
front),  and  the  dorsal  attachment  is  posterior  to  the  ventral 


RESPIRATION'. 


89 


attachment.     Its  general  position  is  shown  in  Figs.  38,  40, 
and  43. 

To  show  the  Action  of  the  Diaphragm  and  Lungs.  —  MATERIAL.  — 
Bell  jar  with  stopper,  sheet  of  rubber  large  enough  to  cover  the  mouth 
of  the  jar,  toy  rubber  balloon,  cork  (rubber  preferred),  glass  tube,  strong 
rubber  band  (such  as  boys  use  for  slung  shots),  marble. 

Triangularis  Sterni 
Internal  Mammary  Vessels       v. 


Left  Phrenic 
Nerve 


Pleura 
Puimonalis 

Pleura  Costalis 


Mediastinum  \  Sympathetic  Nerve 

(  Thoracic  Duct 


Vena  Azygos  Major     I  posterior 
,  Pneumogastric  Nerves  ) 


Fig.  41.    A  Transverse  Section  of  the  Thorax,  showing  the  Relative  Position  of  the 
Viscera  and  Reflections  of  the  Pleurae. 

PREPARATION.  —  Lay  the  marble  on  the  center  of  the  sheet  of  rub- 
ber, double  the  rubber  over  it,  stretching  the  rubber  strongly  over  the 
marble,  and  tie  the  marble  firmly  in  its  place.  Stretch  the  sheet  of 
rubber  over  the  mouth  of  the  jar  with  the  projection  made  by  the  marble 
on  the  outside,  and  fasten  with  rubber  band.  Bore  a  hole  in  the  cork, 


90  PHYSIOLOGY. 

and  fix  the  glass  tube  snugly  in  it,  so  that  the  lower  end  of  the  tube  will 
extend  about  half-way  down  the  jar.  Tie  the  balloon  on  the  lower  end 
of  the  glass  tube. 

EXPERIMENT  i.  —  Inflate  the  balloon.  Consider  that  it  requires 
some  expenditure  of  energy  to  do  this.  When  the  mouth  is  taken  away 
from  the  tube  the  balloon  immediately  collapses. 

EXPERIMENT  2. —  Insert  the  balloon  and  tube  into  the  jar,  but  do 
not  cork,  and  repeat  Experiment  i.  The  same  results  as  before  are 
noticed,  and  it  will  further  be  seen,  or  rather  heard  and  felt,  that  when 
the  balloon  is  inflated  some  air  comes  out  of  the  jar  around  the  tube, 
and  when  the  balloon  collapses  air  again  enters  the  jar. 

EXPERIMENT  3.  —  Again  inflate  the  balloon,  and  while  it  is  inflated 
tightly  cork  the  jar.  If  all  the  parts  fit  well,  the  balloon  should  now 
remain  inflated.  This  may  at  first  seem  strange,  as  the  mouth  is  taken 
away  from  the  tube,  and  the  tube  left  entirely  open  to  the  air.  But  it 
will  be  seen  that  to  just  the  extent  that  the  balloon  contracts,  so  much 
more  space  is  left  in  the  jar  outside  the  balloon.  This  means  diminished 
pressure,  and  the  pressure  of  the  outer  air  presses  the  diaphragm  up, 
and  keeps  the  balloon  partly  distended,  maintaining  equilibrium. 

EXPERIMENT  4.  —  Pull  the  diaphragm  down,  using  the  marble  as  a 
handle.  This  shows  the  expansion  of  the  lung  by  the  pressure  of  the 
external  air  when  more  space  is  given  by  the  depression  of  the  dia- 
phragm. On  releasing  the  diaphragm,  it  springs  upward,  and  the 
balloon  becomes  reduced  in  size,  driving  out  part  of  the  air  that  was  in 
it.  This  shows  how  expiration  is  accomplished,  so  far  as  the  diaphragm 
is  concerned. 

If  a  bell  jar  be  not  at  hand,  a  lamp  chimney  or  a  quart  bottle  may  be 
used,  after  cutting  off  the  bottom,  as  follows  :  File  a  deep  notch  across 
near  the  bottom ;  heat  an  iron  rod,  and  apply  the  end  of  it  to  one  end 
of  the  notch,  and  slowly  draw  the  rod  around  to  the  other  end  of  the 
notch  (the  rod  may  need  to  be  reheated) .  After  cracking  off  the  bot- 
tom of  the  jar,  file  the  edges  so  they  will  not  cut  the  rubber. 

Let  each  pupil  make  a  drawing,  showing  the  position  of  the  parts  in 
inspiration  and  in  expiration. 

Illustration  of  the  Minute  Anatomy  of  the  Lung.  —  To  illustrate 
the  minute  anatomy  of  the  lung,  take  a  rubber  balloon,  a  glass  tube, 
two  rubber  tubes,  one  dyed  red,  the  other  blue,  a  bag  of  netting,  with 
one  side  dyed  red  and  the  other  side  blue.  Tie  the  balloon  on  the  end 
of  the  glass  tube,  slip  the  bag  of  netting  over  the  balloon  and  tie  it, 


RESPrRATION.  91 

with  the  ends  of  the  rubber  tubes  on  the  corresponding  sides  of  the 
bag.  Slip  a  short  piece  of  the  rubber  tube  on  the  end  of  the  glass 
tube,  and  when  the  balloon  is  inflated  shut  the  air  in  by  means  of  a 


CILIA I  i.BRONCHIAL  TUBE. 


Fig.  42.     Minute  Structure  of  the  Lungs,  showing  Air  Vesicles 
and  Capillaries. 

pinchcock.  The  balloon  represents  an  air  vesicle,  the  glass  tube  a 
bronchial  twig,  the  blue  tube  a  subdivision  of  the  pulmonary  artery, 
the  netting  the  capillaries  around  the  vesicle,  and  the  red  tube  one  of 
the  branches  of  the  pulmonary  veins. 

The  Movements  of  Respiration.  —  The  process  of  res- 
piration consists  of  two  acts,  inspiration  and  expiration. 

Two  Active  Forces  in  Inspiration.  —  In  inspiration 
the  principal  active  forces  in  the  body  are,  first,  the  dia- 
phragm ;  and,  second,  the  muscles  which  elevate  the  ribs. 

Work  of  the  Diaphragm  in  Inspiration.  —  The  dia- 
phragm is  a  muscle,  and  when  its  fibers  shorten,  the  dia- 
phragm is  pulled  down.  In  moving  down  it  presses  on 
the  abdominal  organs,  and  makes  the  abdomen  protrude 
laterally  and  ventrally.  This  lowering  of  the  diaphragm 
increases  the  space  in  the  chest ;  the  air  already  in  the 


PHYSIOLOGY. 


chest  expands  to  fill  this  greater  space.  When  expanded 
it  exerts  less  pressure  than  before,  and  the  air  outside, 
having  greater  pressure,  enters  till  equilibrium  is  produced. 
The  air  enters  through  the  trachea,  presses  on  the  inside 
of  the  elastic  lungs,  and  makes  their  bases  extend,  follow- 
ing the  diaphragm  in  its  descent.  The  bases  of  the  lungs 
remain  in  contact  with  the  upper  surface  of  the  diaphragm 
all  the  time. 


. . . .  Increased  Air 
Space 


Inspiration  Expiration 

Fig.  43.    Diagrammatic  Sections  of  the  Body  in  Inspiration  and  Expiration. 

Work  of  the  Chest  Walls  in  Inspiration.  —  Certain 
muscles  of  the  chest  wall  elevate  the,  ribs  and  breast  bone. 
This  act  widens  the  chest,  and  the  air,  as  before,  presses 
in  through  the  open  trachea,  and  keeps  the  sides  of  the 
lungs  in  contact  with  the  inner  surfaces  of  the  chest  walls. 

Effort    required    in    Depressing    the    Diaphragm.  - 
Inspiration  requires  considerable  effort,  because  the  dia- 


RESPIRATION.  93 

phragm  in  its  descent  presses  upon  the  elastic  organs  of 
the  abdomen  (stomach,  liver,  etc.),  and  these  organs,  in 
turn,  are  pressed  against  the  elastic  walls  of  the  abdomen. 
It  is  somewhat  like  pressing  a  pillow  down  into  a  rubber 
bag;  the  pillow  springs  up  as  soon  as  the  pressure  is 
stopped,  because  of  its  own  elasticity  as  well  as  that  of  the 
bag.  Therefore,  as  soon  as  the  diaphragm  relaxes,  the 
elastic  walls  of  the  abdomen  retreat,  and  the  abdominal 
organs  rise  to  their  former  place. 

Effort  Required  in  raising  the  Ribs.  —  When  the  ribs 
are  elevated,  the  cartilages  which  connect  the  ventral  ends 
of  the.  bony  parts  of  the  ribs  with  the  breast  bone  are 
slightly  bent.  When  the  muscles  relax,  the  elasticity  of 
the  rib  cartilages  helps  to  bring  the  ribs  back  to  their 
former  position,  thus  reducing  the  chest  to  its  former 
width. 

Expiration  Easy.  — Thus  we  see  why  expiration  is  easy ; 
in  fact,  "  does  itself "  (in  ordinary  respiration)  by  elastic 
reactions.  But  inspiration  is  harder  than  it  would  be  if  it 
were  not  for  the  fact  that  the  descent  of  the  diaphragm 
meets  resistance,  and  the  ribs,  in  rising,  have  to  overcome 
resistance  in  bending  the  costal  cartilages,  and  in  raising 
the  weight  of  the  chest  walls  and  shoulders. 

Potential  Energy  stored  in  a  Door  Spring.  —  When 
one  opens  a  door  that  has  a  spring  to  shut  it,  he  has  to 
expend  more  energy  to  open  the  door  than  he  would  if  he 
did  not  have  to  bend  (twist  or  compress)  the  spring  at  the 
same  time.  But  no  effort  is  needed  to  shut  the  door.  The 
door  was  opened  and  shut  at  the  same  time ;  i.e.  when 
the  door  was  opened  force  was  stored  in  the  spring  (in  the 
form  of  what  is  called  potential  energy),  and  this  stored 
energy  shuts  the  door  while  we  pass  on.  We  can  better 


94  PHYSIOLOGY. 

afford  to  employ  more  energy  while  opening  the  door  than 
to  take  the  extra  time  to  shut  it.  If,  then,  a  door  with  such 
spring  were  fastened  open,  it  might  remain  open  for  a  long 
time.  When  released  it  flies  shut.  If  one,  in  this  case, 
asks,  "Who  shut  the  door?"  the  answer  is,  "The  person 
who  opened  it." 

The  Storing  of  Energy  during  Inspiration.  —  So  in 

the  act  of  inspiration  we  perform  a  double  work  in  storing 
energy  by  which  the  expiration  is  performed  without  active 
muscular  effort. 

Review  of  Forces  of  Respiration  :  — 

FORCES    OF    INSPIRATION. 

1.  Depression  of  the  diaphragm. 

2.  Muscles  elevating  the  ribs. 

3.  Pressure  of  the  external  air. 

RESISTANCES    TO    INSPIRATION. 

1.  Compression  of  the  abdominal  organs  and  stretching 
abdominal  walls. 

2.  Bending  the  rib  cartilages  and  lifting  the  chest. 

3.  Stretching  the  lungs. 

ELASTIC    REACTIONS    OF    EXPIRATION. 

1.  Elastic  reaction  of  the  abdominal  walls  and  contents. 

2.  Elastic  reaction  of  the  rib  cartilages. 

3.  Elastic  reaction  of  the  lungs. 

Forced  Respiration.  —  Thus  far  we  have  been  speaking 
of  ordinary  respiration.  In  forced  respiration,  as  in  shout- 
ing, many  muscles  are  brought  into  play  to  expel  the  air 
rapidly  and  forcibly.  In  such  an  act  as  coughing  there  is 
vigorous  action  of  the  abdominal  muscles. 


RESPIRATION.  95 

Abdominal  and  Thoracic  Respiration.  —  The  main  part 
of  respiration  is  performed  by  the  diaphragm,  and  the  more 
common  mode  of  respiration  is  therefore  called  abdominal 
or  diaphragmatic  respiration.  In  women  of  the  civilized 
races  respiration  is  more  largely  accomplished  by  the  action 
of  the  thoracic  muscles,  and  is  called  thoracic  or  costal  res- 
piration. In  children  the  respiration  is  of  the  abdominal 
type. 

The  Rate  of  Respiration.  —  The  rate  of  respiration  in 
the  adult  varies  from  sixteen  to  twenty-four  per  minute, 
the  average  being  about  seventeen  times  a  minute ;  about 
one  respiration  for  every  four  heart  beats.  Light  is  favor- 
able to  respiratory  activity.  The  rate  is  affected  by  the 
position  of  the  body,  state  of  activity,  temperature,  diges- 
tion, emotions,  age,  disease,  etc.  Ordinary  inspiration 
takes  slightly  less  time  than  expiration. 

Modifications  of  Respiration.  —  Coughing  is  a  forcible  expiration, 
usually  directed  through  the  mouth,  and  for  the  purpose  of  getting  rid 
of  some  foreign  substance,  or  caused  by  irritation.  In  sneezing  there  is 
first  a  deep  inspiration,  and  then  the  current  of  air  is  forced  out,  chiefly 
through  the  nose.  Sneezing  may  be  prevented  by  pressing  firmly  on 
the  upper  lip.  Crying,  laughing,  sobbing,  are  modifications  of  respira- 
tion connected  with  certain  emotions.  Yawning  and  sighing  are  deeper 
breathings,  caused  by  etijiui,  depressing  emotions,  or  a  deficient  ventila- 
tion. Hiccuping  is  sudden  inspiration,  produced  by  spasmodic  action 
of  the  diaphragm,  accompanied  by  sudden  closure  of  the  glottis,  and  is 
often  caused  by  some  disorder  of  stomach  digestion.  Snoring  is  caused 
by  breathing  through  the  mouth  and  setting  the  soft  palate  into  vibra- 
tion. Sniffing  is  sudden  inspiration  :  the  diaphragm  is  suddenly  pulled 
down,  the  air  in  the  nasal  cavity  is  thus  drawn  downward,  and  the  air 
we  wish  to  test,  or  the  odor  we  wish  to  inhale,  is  thus  drawn  into  the 
upper  nasal  cavities ;  whereas  in  ordinary  inspiration  most  of  the  air 
passes  along  the  lower  part  of  the  nasal  passage.  In  hawking,  the  air 
is  forced  out  through  the  narrowed  passage  between  the  root  of  the 
tongue  and  the  soft  palate  to  remove  mucus.  Gargling  is  forcing  air  up 


96  PHYSIOLOGY. 

through  liquid  held  between  the  tongue  and  the  soft  palate.  Panting, 
whistling,  blowing,  spitting,  sucking,  and  drinking  are  also  modifica- 
tions of  respiration.  In  case  of  choking  it  is  well  to  hold  the  head  for- 


Jl 

II 


COMPLEMENTAL  AIR. 

120   CUBIC  INCHES. 
AIR    THAT  CAN   BE   BUT  SELDOM    IS    TAKEN  IN. 


TIDAL    AIR.— 20  to  30  Cubic  Inches  Air  Taken  in 
and  Sent  out  at  Each  Breath. 


RESERVE  AIR. 

100   CUBIC  INCHES. 


m 

^  AIR    THAT  CAN   BE  BUT  IS   SELDOM   DRIVEN   OUT. 


RESIDUAL   AIR. 


100   CUBIC   INCHES. 


AIR   THAT  CANNOT  BE  DRIVEN   OUT. 


II 

t> 

-S  -S 


- 


QU 


Figr.  44.     Diagram  of  Lung  Capacity. 

ward,  and  perhaps  downward.  A  smart  slap  between  the  shoulders 
sometimes  helps  dislodge  anything  stuck  in  the  throat,  and  it  may  be 
necessary,  in  addition,  to  hold  a  child  with  its  head  downward. 


RESPIRATION.  97 

Capacity  of  the  Lungs.  —  Have  the  class  stand,  and  each  pupil  raise 
his  right  hand. 

1 .  Tidal  Air.  —  Let  all  breathe  together,  at  the  ordinary  rate  and 
depth,  and  let  the  hand  rise  about  three  inches  during  inspiration,  and 
fall  again  during  expiration.     The  amount  of  air  taken  in  at  an  ordinary 
breath  is  from  20  to  30  cubic  inches,  or  about  a  pint.     This  is  called 
tidal  air. 

2.  Complemental  Air.  —  As  before,  let  the  hand  go  up  and  down 
with  the  breathing,  but  at  the  end  of  the  third  inspiration,  instead  of 
stopping  with  the  usual  amount,  keep  on  breathing  in  as  much  as  pos- 
sible, letting  the  hand  rise  accordingly.     This  air  that  can  be  taken  in 
above  the  ordinary  breath  is  called  the  complemental  air,  and  it  is 
estimated  to  be,  on  the  average,  about  120  cubic  inches. 

3.  Reserve  Air.  —  Begin  as  before,  and  at  what  would  be  the  end 
of  the  third  expiration  continue  to  drive  out  as  much  air  as  possible, 
indicating  the  degree  by  correspondingly  lowering  the  hand.     This  air 
that  can  be  breathed  out  beyond  the  ordinary  expiration  is  called  the 
reserve  air,  and  is  reckoned  at  about  100  cubic  inches. 

4.  Residual  Air. —  The  air  cannot  all  be  breathed  out.     The  re- 
mainder is  called  the  residual  air,  and  is  computed  to  be  about  100 
cubic  inches. 

The  Vital  Capacity.  —  All  the  air  that  can  be  breathed  out  after  a 
full  inspiration,  i.e.  the  sum  of  the  complemental,  tidal,  and  reserve 
air,  would  be  about  240  to  250  cubic  inches,  and  is  called  the  vital 
capacity.  Of  course  these  figures  represent  only  the  average  of  cer- 
tain experiments  and  observations.  By  practice  any  one  can  con- 
siderably increase  his  vital  capacity. 

A  Test  of  the  Capacity  of  the  Lungs. —  A  simple  method  of 
measuring  these  stages  of  respiration  is  to  take  a  gallon  bottle  and 
first  carefully  graduate  it  to  pints  by  pouring  in  water  and  marking  on 
the  outside  with  a  file.  Then  invert  the  bottle  in  a  trough  of  water, 
and  inhale  from  it  by  means  of  a  rubber  tube.  Or  fill  the  bottle,  in- 
vert in  water,  and  exhale  into  it. 

Hygiene  of  Breathing.  —  Those  persons  who  take  con- 
stant exercise  in  the  open  air  are  likely  not  to  suffer  much 
from  deficient  respiration.  But  persons  following  seden- 


98  PHYSIOLOGY. 

tary  occupations,  such  as  that  of  the  student,  not  calling 
for  deep  breathing  (and  often  the  air  taken  in  is  of  poor 
quality),  need  to  pay  especial  attention  to  the  matter. 

Breathing  through  the  Mouth.  —  We  should  breathe 
through  the  nose,  and  not  through  the  mouth.  The  nasal 
passages  are  fitted  for  the  introduction  of  the  air  (i)  by 
being  narrow,  but  of  large  area;  (2)  by  having  their  lining 
membranes  richly  supplied  with  blood ;  (3)  by  the  abun- 
dant secretion  of  mucus  by  this  membrane.  The  air, 
coming  through  this  narrow  channel,  is  warmed,  and  a 
large  part  of  any  dust  it  may  contain  is  caught  by  the 
sticky  mucus  that  covers  all  the  walls  of  this  passageway. 
If  we  breathe  through  the  mouth  (especially  out  of  doors 
in  cold  weather),  the  air  may  not  be  sufficiently  warmed 
before  entering  the  lungs,  and  much  more  dust  would  be 
carried  into  the  lungs.  Then,  too,  the  air  has  a  drying 
effect  on  the  throat,  whereas  the  mucus  of  the  nasal  pas- 
sages will  moisten  the  air  as  it  enters.  The  cilia,  which 
extend  from  most  of  the  cells  lining  the  respiratory  pas- 
sages, are  constantly  causing  the  mucus  to  slowly  flow 
toward  the  external  opening,  so  a  good  share  of  the  dust 
is  gotten  rid  of.  A  further  advantage  of  breathing  through 
the  nose  is  that  we  detect  odors,  and  can  thus  judge  of  the 
quality  of  the  air. 

Breathing  and  Circulation.  —  The  fact  has  been  noted 
that  breathing  directly  aids  the  circulation  of  the  blood. 
This  is  due  to  the  way  air  pressure  is  made  to  affect  the 
large  veins.  Breathing  also  may  very  considerably  aid 
the  flow  of  lymph.  Every  deep  inspiration  brings  pres- 
sure to  bear  on  the  main  lymph  duct  as  the  diaphragm 
descends.  Every  forced  expiration  has  the  same  effect. 
We  must  keep  in  mind  that  the  tissues  are  fed  directly  by 


RESPIRATION.  99 

the  lymph  that  surrounds  them ;  that  while  the  lymph  is 
continually  fed  by  the  blood,  there  is  not  a  great  pressure 
given  in  this  way.  The  lymph  stream  is  largely  depend- 
ent on  the  pressure  of  the  surrounding  organs.  When 
one  takes  a  good  deal  of  muscular  exercise  the  lymph  is 
renewed  with  rapidity  enough  to  supply  the  tissues  with 
food,  and  to  carry  away  their  wastes.  But  in  those  who 
sit  quiet  a  large  share  of  the  day,  taking  no  more  exercise 
than  is  necessary  to  take  them  to  and  from  their  places 
of  business,  the  lymph  becomes  too  nearly  stagnant,  the 
tissues  are  not  well  nourished,  and  the  whole  body  suffers. 

Deep  Breathing.  —  It  is  a  grateful  relief  to  the  whole 
system  to  stand,  stretch,  inhale  deeply  and  slowly  several 
times,  and  to  repeat  this  every  hour  or  so.  Every  one  en- 
gaged in  office  work  or  studying  should  form  this  habit, 
especially  if  he  does  not  give  an  hour  daily  to  exercise  in 
a  gymnasium,  or  otherwise. 

Respiratory  Sounds.  —  During  respiration  sounds  are 
produced  by  which  the  skilled  physician  can  tell  much  as 
to  the  condition  of  the  respiratory  organs. 

The  Control  of  Respiration.  —  Breathing  is  an  involun- 
tary act.  Still  we  can  modify  it.  We  can  hold  the  breath 
for  a  time ;  but  it  is  stated  that  one  cannot  hold  the  breath 
long  enough  to  produce  death  by  suffocation. 

The  muscles  of  respiration  are  under  the  control  of 
nerves.  The  center  of  respiratory  control  is  believed  to 
be  in  the  lower  portion  of  the  spinal  bulb.  This  respira- 
tory center  is  one  of  the  most  vital  points  in  the  body,  for 
if  it  is  destroyed,  breathing  is  completely  stopped,  and 
death  ensues.  This  center  is  affected  by  the  condition  of 
the  blood.  For  instance,  if  the  blood  going  to  this  center 
has  not  enough  oxygen,  the  center  hastens  the  process 


100  PHYSIOLOGY. 

of  breathing  by  nerve  impulses  sent  to  the   muscles  of 
respiration. 

The  Control  of  the  Diaphragm.  —  The  diaphragm  is 
under  the  control  of  the  phrenic  nerves,  which  arise  from 
the  third,  fourth,  and  fifth  cervical  nerves.  If  the  neck  is 
broken  above  the  point  where  these  nerves  are  given  off, 
death  almost  always  immediately  follows,  because  the  con- 
nection of  the  respiratory  center  and  the  diaphragm  is 
broken. 

Composition  of  Dry  Air  (by  volume)  :  — 

Oxygen      .     .     .     .     .     .     ....     .     2 1 .00 

Nitrogen    .     .     .     .     .    v    .     .     .     .     .     79.00  . 

Carbon  Dioxid .04 

100.04 

Experiments  illustrating  the  Chemistry  of  Respiration.  —  EX- 
PERIMENT i .  —  If  a  piece  of  phosphorus  be  burned  under  a  fruit  jar 
inverted  and  with  the  mouth  under  water  (for  directions  consult  any 
chemistry),  the  oxygen  will  be  consumed  and  water  will  enter  part  way 
to  take  its  place.  The  remainder  is  nitrogen. 

EXPERIMENT  2.  —  If  a  burning  taper  be  lowered  into  this  nitrogen, 
the  flame  will  be  extinguished. 

EXPERIMENT  3.  —  If  a  chemical  laboratory  is  at  hand,  some  carbon 
dioxid  should  be  generated  and  tested  to -show  that  it  extinguishes 
flame. 

EXPERIMENT  4.  —  Lime  water  is  the  test  of  carbon  dioxid,  and  may 
easily  be  prepared  by  putting  a  piece  of  quicklime  the  size  of  a  hen's 
egg  into  a  quart  of  water. 

EXPERIMENT  5.  —  Pour  a  little  clear  lime  water  into  a  jar  contain- 
ing carbon  dioxid,  and  on  shaking  the  contents  the  lime  water  will  be 
rendered  milky. 

EXPERIMENT  6.  —  By  means  of  a  tube  (a  straw  will  serve)  breathe 
through  a  small  quantity  of  lime  water  to  show  that  there  is  carbon 
dioxid  in  the  expired  breath. 

EXPERIMENT  7.  —  If  a  jar  be  inverted  over  a  lighted  taper,  the  flame 
will  soon  be  extinguished.  Test  the  gas  with  lime  water  to  see  that 
carbon  dioxid  is  produced  by  a  burning  candle. 


RESPIRATION.  IOI 

EXPERIMENT  8.  —  By  holding  a  clean,  cold  tumbler  over  a  burning 
taper  it  will  be  seen  that  water  vapor  is  produced  by  the  burning. 

EXPERIMENT  9.  —  Breathing  into  a  clean,  cold  tumbler  shows  that 
water  is  produced  also  in  the  process  of  respiration. 

EXPERIMENT  10.  —  A  very  brilliant  experiment  and  one  that  is  very 
instructive  at  this  point  is  to  burn  a  watch  spring  in  oxygen.  In  this 
process  the  oxygen  unites  with  the  iron,  forming  iron  oxid. 

EXPERIMENT  n.  —  If  a  piece  of  watch  spring  be  placed  in  water,  it 
will  soon  rust.  Rust  is  also  an  iron  oxid,  only  the  process  is  slow, 
instead  of  rapid  as  in  the  case  of  combustion,  and  just  as  much  heat  is 
given  off,  but  not  much  at  any  given  instant. 

EXPERIMENT  12.  —  If  a  short  piece  of  magnesium  ribbon  can  be 
obtained,  it  may  be  burned  in  the  presence  of  the  class,  though  it  is  not 
well  to  look  long  at  the  excessively  strong  while  light. 

EXPERIMENT  13.  —  Ma£nMslimi;wild  also 'ru^'in  water,  forming  a 
white  rust,  or  magnesium  oxid,  as  in  burning.  ,  ,  ,  , 

EXPERIMENT  14.  —  If  a  <fer  be  ftlz&  whVthfi  jsScwiy  expired  breath, 
capped  tightly,  and  set  in  a  warm  place  it  will  acquire  a  bad  odor. 

EXPERIMENT  15.  —  Hold  a  thermometer  at  arm's  length.  It  indi- 
cates the  temperature  of  the  air  —  of  the  air  that  you  are  breathing  in. 
Breathe  for  a  few  minutes  upon  the  bulb  of  the  thermometer,  and  the 
fact  is  clearly  shown  that  the  air  we  breathe  out  is  much  warmer  than 
the  air  that  we  breathe  in. 

EXPERIMENT  16.  — With  a  pair  of  bellows  force  the  air  of  the  room 
through  a  small  quantity  of  lime  water.  By  continuing  this  process  a 
long  time  it  may  be  shown  that  there  is  carbon  dioxid  in  the  air,  but  not 
nearly  so  much  as  in  the  expired  breath. 

Result  of  Experiments.  — These  experiments  show  that 
breathed  air  has  gained  :  — 

1.  Heat. 

2.  Water  vapor. 

3.  Carbon  dioxid. 

4.  Waste   products,   or   impurities,   having   no    definite 
name,  because  not  well  known,  highly  putrescible,  often 
called  by  the  general  name  of  ''organic  waste  matter." 


102 


PHYSIOLOGY. 


IN  10,000  VOLUMES. 

i  Represented  by  Largo  Square.) 

PER  CENT. 


AMOUNT  OF  CARBON 

DIOXID. 

IN 

INSPIRED  AIR.     EXPIRED  AIR. 


4  400 

(Small  Square.)     (Medium  Square). 

.04  4 


COMMON  FRACTION  —^~ 

r 


25 


20  100 

Fig.  45.    Amount  of  Carbon  Dioxid  in  Inspired  and  Expired  Air. 

The  Composition  of  Inspired  and  Expired  Air.  - 

Oxygen.     Nitrogen.     Carbon  Dioxid. 
Inspired  air     ...         21  79  .04 

Expired  air     ...         16  79  4.00 


While  the  amount  of  nitrogen  remains  about  the  same, 
some  oxygen  has  disappeared,  and  its  place  is  taken  by 
carbon  dioxid,  while  the  amount  of  carbon  dioxid  has  in- 
creased a  hundred-fold. 


RESPIRATION. 


103 


Exchanges  between  the  Air  and  the  Blood  in  the 
Lungs. — Whatever  the  air  coming  from  the  lungs  cen- 
tains  that  was  not  in  the  air  entering  them,  it  has  taken 
from  the  blood,  and  what  the  air  has  lost  it  has  given  to 
the  blood.  The  air  in  the  air  vesicle  is  separated  from  the 


BRONCHIAL  TUBE 


FROM  PULMONARY  ARTERY 


TO  PULMONARY  VEIN 


Fig.  46.     Exchanges  between  the  Air  and  the  Blood  in  the  Lungs. 

blood  in  the  pulmonary  capillaries  only  by  the  thin  wall  of 
the  air  vesicle  and  the  thin  capillary  wall.  Carbon  dioxid, 
water,  and  other  waste  matters  pass  from  the  blood  through 
this  thin  partition  into  the  air  vesicle,  to  be  sent  out  by 
later  expiration.  Oxygen  from  the  air  in  the  vesicle  passes 


104  PHYSIOLOGY. 

through  these  layers  into  the  plasma,  and  most  of  it  is 
quickly  picked  up  by  the  colored  corpuscles.  The  colored 
corpuscles  are  the  carriers  of  oxygen. 

Hemoglobin  and  Oxy hemoglobin.  —  As  has  already 
been  stated,  the  hemoglobin  in  the  colored  corpuscles  has 
an  affinity  for  oxygen.  Hemoglobin  is  of  a  dark  color, 
and  gives  the  dark  color  to  the  blood  which  enters  the 
lungs.  When  oxygen  unites  with  the  hemoglobin  it  forms 
oxyhemoglobin,  which  is  of  a  bright  red  color.  Hence 
the  change  in  the  color  of  the  blood  in  the  lungs  from  a 
dark  bluish  red  to  a  bright  scarlet.  This  bright  blood  is 
usually  called  "arterial,"  and  the  dark  "venous";  but  it 
must  be  remembered  that  the  blood  in  the  pulmonary 
artery  is  dark,  and  in  the  pulmonary  veins  bright. 

Amount  of  Oxygen  Used. —We  take  into  the  blood 
only  about  one  fourth  of  the  oxygen  of  the  air  that  passes 
through  the  lungs.  In  like  manner  the  blood,  passing 
through  the  tissues,  gives  up  to  those  tissues  (in  ordinary 
circumstances)  only  about  half  the  oxygen  it  contains  (per- 
haps holding  the  remainder  as  a  reserve). 

The  Gases  in  the  Blood.  —  If  a  quart  of  blood  be  placed 
under  the  receiver,  and  the  air  exhausted,  it  will  be  found 
that  the  blood  contained  about  three  fifths  of  a  quart  of 
gas.  This  gas  is  a  mixture  of  oxygen,  carbon  dioxid,  and 
nitrogen,  and  the  proportions  vary  according  to  the  kind 
of  blood  taken.  If  from  the  left  heart,  or  pulmonary  veins, 
there  will  be  more  oxygen  and  less  carbon  dioxid ;  if  from 
the  right  heart,  pulmonary  artery,  or  caval  veins,  there 
will  be  less  oxygen  and  more  carbon  dioxid.  Oxyhemo- 
globin blood  ("arterial  blood  ")  contains  about  one  fifth  its 
volume  of  oxygen.  Hemoglobin  blood  ("venous  blood") 
contains  about  one  tenth  its  volume  of  oxygen.  Oxy- 


RESPIRATION. 


105 


hemoglobin  blood  holds  about  two  fifths  its  bulk  of  carbon 
dioxid,  while  hemoglobin  blood  has  nearly  one  half  its 
bulk  of  carbon  dioxid. 


,  THE   GASES   IN  THE   BLOOD. 

From  100  volumes  of—  May  be  obtained 


Oxygen.    Carbon  dioxid.     Nitrogen. 

Oxyhemoglobin  (arterial)  blood  .    2ovols.  /pvols.          ito2vols. 

Hemoglobin  (venous)  blood    .     .    lovols.  46vols.          ito2vols. 

Illustration  of  the  Changes  in  the  Color  of  the  Blood. —  The 

changes  that  take  place  in  the  color  of  the  blood,  both  in  the  lungs 
and  in  the  tissues  of  the  other  parts  of  the  body,  may  be  illustrated  as 


Fig.  47. 

follows  :  Prepare  a  heart  as  directed  on  page  45.  Use  for  the  liquid  a 
strong  solutiofl  of  litmus,  neutralized  or  slightly  alkaline ;  place  in  the 
throat  of  each  funnel  a  small  sponge.  Saturate  with  ammonia  the 
sponge  in  the  funnel  representing  the  capillaries  of  the  body,  and 


106  PHYSIOLOGY. 

saturate  with  hydrochloric  acid  the  one  in  the  funnel  representing  the 
capillaries  of  the  lungs. 

Now,  on  working  the  heart  the  liquid  will  change  from  red  to  blue 
in  the  funnel  representing  the  body,  and  from  blue  to  red  in  the  funnel 
representing  the  lungs. 

"  Anatomically  there  are  two  lungs,  and  the  heart  lies  between  them  ; 
physiologically,  the  lungs  form  a  single  organ,  which  is  interposed  be- 
tween the  two  hearts."  —  WILDER. 

The  Changes  in  the  Blood. — What  does  the  blood  do 
with  the  oxygen  that  it  gets  in  the  lungs,  and  where  did  it 
get  the  carbon  dioxid  and  other  impurities  that  it  brings 
to  the  lungs  ?  Let  us  follow  the  blood  and  see.  From 
the  pulmonary  veins  the  blood  goes  to  the  left  heart,  and 
is  pumped  to  all  the  tissues  except  the  lungs.  Let  us- 
follow  a  branch  of  the  aorta  that  leads  to  a  muscle. 

The  Production  of  Heat  and  Motion  in  the  Body.  - 

When  a  muscle  works  it  becomes  warmer.  This  has  been 
repeatedly  proved  by  experiment.  We  know  that  we  feel 
warmer  when  we  exercise.  We  know  that  the  blood  is 
flowing  more  rapidly  through  the  muscle  when  it  is  at 
work.  This  more  rapid  stream  brings  the  muscle  more 
oxygen.  This  it  needs,  for  the  heat  of  the  muscle  is  pro- 
duced by  the  oxidation  of  substance  in  the  muscle.  We 
have  seen  that  the  oxidation  of  iron  produces  heat,  and  it 
is  the  oxidation  of  the  materials  in  the  candle  that  enable 
it  to  give  out  heat.  But  our  bodies  do  not  give  out  the 
intense  heat  of  a  burning  candle,  nor  do  they  produce 
light,  as  is  the  case  with  the  oxidation  of  iron  and  magne- 
sium when  those  metals  are  burned.  The  slow  oxidation 
of  the  metals,  in  the  presence  of  moisture,  is  more  like 
the  oxidations  in  our  bodies.  It  is  by  the  oxidations  of 
the  muscle  (or  substance  in  it)  that  the  muscles  produce 
heat  and  that  form  of  energy  which  gives  motion.  In  the 


RESPIRATION. 

Case  of  the  rusting  of  the  metals  there  is  as  much  heat  pro- 
duced as  when  they  are  burned,  but  the  heat  is  so  slowly 
generated  that  it  is  given  off  about  as  fast  as  it  is  pro- 
duced, and  we  do  not  notice  it.  The  oxidation  produces 
the  waste  matters,  just  as  the  burning  of  the  various 
substances  produces  waste. 

Oxidation  of  Live  Tissues  and  Dead  Matter.  —  In  our 

experiments  with  oxygen  we  see  that  substances  which 
burn  in  air  will  burn  still  more  actively  in  oxygen.  But 
we  must  not  infer  from  this  that  in  our  bodies  the  oxida- 
tion of  the  tissues  would  be  faster  in  pure  oxygen.  This 
is  not  the  case.  The  tissues  take  as  much  oxygen  as  they 
need  (if  they  can  get  it),  and  they  will  not  take  any  more 
than  they  need,  no  matter  how  much  is  offered  them.  It 
does  not  injure  the  body,  nor  any  part  of  it,  to  breathe 
pure  oxygen.  It  does  not  make  one  feverish,  it  does  not 
produce  any  more  heat,  nor  make  one  "live  faster."  This 
point  should  be  specially  noticed,-  as  it  was  formerly  sup- 
posed that  the  oxidation  of  the  tissues  of  the  body  was 
just  like  any  combustion  of  dead  material.  But  the  tissues 
are  alive.  They  know  their  own  needs.  Each  cell  takes 
what  it  requires  and  no  more,  just  as  it  does  of  food 
brought  to  it  by  the  blood.  The  amount  of  oxygen  pres- 
ent does  not  determine  the  degree  of  muscular  activity, 
but  the  degree  of  muscular  activity  determines  the  amount 
of  oxygen  consumed. 

Increased  Blood  Flow  is  the  Result  of  Exercise.  - 
When  we  exercise,  the  muscles  need  more  oxygen.  They 
also  need  to  have  removed  the  waste  matters  that  they  are 
so  rapidly  producing  at  this  time.  How  is  the  oxygen 
brought  and  the  waste  removed  ?  By  the  blood,  you 
answer.  True ;  but  what  makes  the  blood  come  and 


I08  PHYSIOLOGY. 

go  faster  at  this  time  ?  By  reflex  action,  you  reply.  The 
muscles  send  a  message  to  a  nerve  center,  and  this  nerve 
center  sends  back  a  message  to  the  blood  tubes,  making 
them  widen,  and  the  heart  also  may  be  made  to  beat 
faster.  But  would  it  do  any  good  to  have  the  blood  flow 
through  the  muscles  faster,  if  it  could  not  bring  more  oxy- 
gen, and  take  away  and  get  rid  of  more  wastes  ?  You 
will  say  no.  To  give  the  extra  oxygen,  and  take  out  the 
carbon  dioxid,  the  lungs  cannot,  of  themselves,  take  in  and 
send  out  air.  The  work  of  pumping  air  depends  on  the 
muscles  of  respiration,  the  diaphragm,  and  the  muscles 
that  elevate  the  ribs.  These  will  not  work  faster  unless 
they  are  ordered  to  do  so.  A  message  must  be  sent  to 
these  telling  of  the  need  in  the  muscles  that  we  are  con- 
sidering, say  one  of  the  large  muscles  of  the  lower  limbs. 
Thus,  by  a  series  of  reflex  actions,  all  these  processes  are 
kept  in  harmonious  relation  to  each  other.  It  must  be 
borne  in  mind  that  increased  blood  flow  is  the  conse- 
quence, and  not  the  cause,  of  the  increased  activity  of  the 
tissues. 

Temperature  of  the  Body.  —  Insert  the  bulb  of  a  thermometer  into 
the  mouth,  and  keep  it  there  three  or  four  minutes  to  find  the  tempera- 
ture of  the  inside  of  the  body.  For  this  it  is  better  to  use  a  clinical 
thermometer,  if  one  can  be  obtained.  The  average  temperature  of  the 
tissues  within  the  body  is  about  98.5°  F. 

How  the  Body  is  like  a  Stove.  —  The  body  may  be 
compared  to  a  stove.  Into  one  we  put  fuel  and  produce 
heat.  In  the  other  we  get  heat  from  food. 

How  the  Body  differs  from  a  Stove.  —  But  the  body  is 
not  like  the  stove  in  burning  the  fuel  (food)  directly.  The 
food  is  first  made  into  tissues,  or  "  storage  compounds  "  in 
the  tissues.  It  is  as  though  we  were  to  build  a  stove 


RESPIRA  T1ON.  1 09 

entirely  of  coal,  and  then  start  a  fire  in  it.  In  that  case  it 
would  produce  heat  not  merely  by  burning  in  one  place 
within,  but  would  be  burning  throughout  the  whole  of  its 
substance.  This  is  the  case  with  the  body. 

Oxidation  in  Tissue  the  Source  of  Heat  in  the  Body.  - 

We  have  seen  that  the  muscles  constitute  nearly  half  of 
the  weight  of  the  body.  We  know,  too,  that  they  are  more 
active  than  most  of  the  tissues.  We  would  now  naturally 
infer,  as  indeed  is  the  fact,  that  they  are  the  chief  source 
of  the  heat  produced  in  our  bodies. 

The  tissues  of  the  body  are  oxidizing  all  the  time.  But 
when  they  are  in  vigorous  action  they  oxidize  very  much 
more  rapidly. 

Next  to  the  muscles,  in  importance  as  a  heat  producer, 
is  the  liver,  which  is  the  largest  gland  in  the  body,  and,  as 
we  shall  soon  see,  one  of  the  most  active.  The  blood,  as 
it  leaves  the  liver  by  the  hepatic  vein,  is  hotter  than 
anywhere  else  in  the  body. 

How  the  Body  is  like  a  Locomotive.  —  But  it  will  be 
better  to  compare  the  body  to  a  locomotive,  as  we  produce 
not  only  heat,  but  motion  as  well. 

If  a  visitor  from  another  planet,  unfamiliar  with  such 
creatures  as  we  are,  were  to  observe  closely  a  man  and  a 
locomotive,  he  would  see  several  points  in  common  :  — 

1.  Both  are  warm. 

2.  Both  move. 

3.  Both  use  fuel  (food  or  coal). 

4.  Both  take  in  air,  and  (if  it  were  a  winter  day) 

5.  Both  give  off  smoke  (which  is  essentially  the  same 
in  the  two,  carbon  dioxid  and  water  vapor  being  the  chief 
constituents). 


no  PHYSIOLOGY. 

How  the  Body  differs  from   a   Locomotive.  —  By  a 

closer  examination  he  would  find  out  some  of  the  differ- 
ences that  we  have  noticed  :  — 

1.  That  the  body  does  not  get  hot  enough  to  burn  ;  i.e. 
the  oxidation  is  relatively  slow,  and  is  not  combustion. 

2.  That  the  oxidation  of  the  body  never  produces  light. 

3.  That  the  oxidation  here  is  always  in  the  presence  of 
moisture. 

The  Amount  of  Carbon  Dioxid  given  off. — When  the 
breath  is  held  for  some  time,  the  carbon  dioxid  in  the  ex- 
pired air  may  reach  7  or  8  per  cent.  During  violent 
exercise  the  amount  of  carbon  dioxid  given  off  may  be 
from  two  to  two  and  a  half  times  as  much  as  when  we  are 
at  rest.  The  amount  of  carbon  dioxid  given  off  is  in- 
creased in  cold  weather,  and  by  taking  food,  and  decreased 
from  one  fifth  to  one  fourth  during  sleep.  Oxygen  is 
carried  chiefly  in  the  corpuscles,  but  the  carbon  dioxid  is 
carried  in  both  plasma  and  corpuscles. 

Storage  of  Oxygen  in  the  Tissues.  —  The  activity  of  the  tissues 
from  their  oxidation  does  not  necessarily  mean  that  the  oxidation  is 
direct ;  that  is,  that  the  oxygen  is  used  as  soon  as  it  is  brought  to  the 
tissue.  For  instance,  in  the  muscles  it  is  believed  that  the  oxygen  is 
stored  in  some  form,  probably  in  combination,  so  that  it  can  be  used 
when  needed,  perhaps  much  more  rapidly  than  could  be  supplied  by  the 
respiration  at  the  time.  If  we  study  the  chemistry  of  explosion,  we 
learn  that  it  is  a  very  rapid  combustion.  In  the  explosives  are  ma- 
terials that  unite  instantaneously,  instead  of  slowly  burning,  as  in  the 
case  of  ordinary  combustibles. 

The  Action  of  Muscles  like  an  Explosion.  —  Now,  many  physiolo- 
gists hold  that  a  sort  of  explosive  compound  is  formed  in  the  muscles, 
and  that  when  the  muscle  acts  it  does  so  as  the  result  of  the  explosion, 
so  to  speak,  of  this  material.  And,  to  carry  out  the  figure,  the  nerve  is 
compared  to  the  match  that  ignites  the  explosive.  A  little  heat  is 
enough  to  cause  the  most  violent  explosion.  So  the  force  that  passes 


RESTIRA  77  ON.  1 1 1 

along  a  nerve  fiber  is  slight.  But  it  rouses  a  great  amount  of  energy 
that  lay  dormant  in  the  muscle.  It  would  seem  to  have  "touched  off11 
a  lot  of  explosive  material  that  was  already  there,  rather  than  merely 
started  an  action  that  depends  on  the  comparatively  slow  process  of 
respiration  at  the  time.  We  cannot  follow  this  theory  farther,  as  it 
takes  us  too  deep  into  the  study  of  chemistry  in  its  most  difficult 
branch,  —  physiological  chemistry. 

Summary  of  Respiration.  —  The  tissues  need  oxygen  ; 
air  is  pumped  into  the  lungs ;  this  air  gives  oxygen  to  the 
blood ;  the  blood  carries  it  to  the  tissues. 

In  oxidizing,  the  tissues  produce  energy  (heat  and  mo- 
tion) and  give  off  waste  matter  (water,  carbon  dioxid,  etc.); 
these  the  blood  carries  to  the  lungs,  the  lungs  give  them 
to  the  air,  and  the  air  carries  them  out  of  the  body. 

The  pumping  of  the  air  in  and  out  may  be  called  "  me- 
chanical respiration."  The  changes  between  the  air  and 
the  blood  in  the  lungs  we  will  call  the  "  ventilation  of  the 
blood,"  and  the  interaction  of  the  blood  and  the  tissues 
the  "real,  or  internal  respiration." 

The  Two  Breaths.  — "  Every  time  you  breathe  you 
breathe  two  different  breaths ;  you  take  in  one,  you  give 
out  another.  The  composition  of  these  two  breaths  is 
different.  Their  effects  are  different.  The  breath  which 
has  been  breathed  out  must  not  be  breathed  in  again. "- 
KINGSLEY. 

Breathing  Expired  Air. —  The  air  in  the  vesicles  re- 
ceives from  the  blood  carbon  dioxid,  water  vapor,  and 
other  impurities  above  mentioned.  It  has  been  believed 
for  a  number  of  years  that  the  organic  impurities  consti- 
tute the  most  dangerous  element  in  expired  air.  Carbon 
dioxid,  though  to  some  extent  a  poison,  is  not  very  injuri- 
ous in  such  quantities  as  ordinarily  exist  in  the  air,  even  in 
poorly  ventilated  rooms ;  while  the  headache  and  drowsi- 


112  rilYSlOLOGY. 

ness  that  one  experiences  in  a  close  room  where  there  are 
a  number  of  people  is  due  to  the  reabsorption  of  these  or- 
ganic matters.  It  is  not  due  to  lack  of  oxygen,  for  the 
oxygen  may  be  reduced  to  13  per  cent  without  causing 
discomfort.  A  person  may  breathe  air  containing  i  per 
cent  of  carbon  dioxid,  with  a  corresponding  reduction  of 
oxygen,  when  the  carbon  dioxid  is  generated  by  ordinary 
chemical  processes  (as  in  a  small  room  with  a  large  kero- 
sene lamp,  or  a  gasoline  stove);  but  air  having  I  per 
cent  of  carbon  dioxid  produced  by  breathing  is  highly  in- 
jurious, because  it  contains  the  organic  impurities  above 
noted,  and  the  term  "crowd  poison"  has  been  employed 
for  this  material.  Later  investigators,  however,  maintain 
that  there  is  nothing  injurious  in  the  freshly  expired  breath. 


Summary. —  i.  In  the  lungs  the  air  and  blood  are  brought  very 
close  together,  only  the  wall  of  the  capillary  and  that  of  the  air  vesicle 
intervening. 

2.  Through  these  two  layers  oxygen  passes  from  the  air  vesicle 
into  the  blood.     Carbon  dioxid,  water  vapor,  ancj  other  wastes  pass 
from  the  blood  into  the  air  vesicle. 

3.  The   mucous   membrane  of  the  air  passages   secretes   mucus 
which  is  driven  toward  the  nostrils  by  the  cilia. 

4.  The  chest  is  lengthened  by  the  depression  of  the  diaphragm, 
and  widened  by  the  elevation  of  the  ribs,  giving  greater  space,  which  is 
filled  by  external  air  expanding  the  lungs. 

5.  Inspiration  acts  in  opposition  to  resistances,  whose  elastic  re- 
action performs  ordinary  expiration  without  active  effort. 

6.  There  are  four  heart  beats  for  each  respiration. 

7.  The  lungs  are  never  emptied. 

8.  Respiratory  capacity  may  be  increased  by  exercise  and  practice. 

9.  Respiration  is  controlled  by  the  nervous  system  ;  the  respiratory 
center  is  in  the  spinal  bulb. 

10.  Internal  respiration  is  an  oxidation  in  the  tissues,  illustrated  by 
the  rusting  of  moist  iron. 


RES  PI R  A  TION.  1 1 3 

11.  In  passing  through  the  lungs  air  loses  oxygen,  and  gains  water, 
carbon  dioxid,  and  other  wastes. 

12.  Oxygen  is  carried  chiefly  by  the  colored  corpuscles  of  the  blood  ; 
it  unites  with  hemoglobin  in  the  corpuscles,  forming  oxyhemoglobin, 
and  gives  the  blood  its  bright  scarlet  color. 

13.  The  energy  of  heat  and  motion  in  the  body  results  from  the 
oxidations  in  the  tissues. 

14.  Air  once  breathed  is  unwholesome.    The  air  of  living  and  sleep- 
ing rooms  needs  constant  renewal. 

Questions.  —  i .   Is  it  a  good  thing  to  see  how  long  one  can  hold  his 
breath  ? 

2.  Should  the  head  be  covered  by  bedclothes  ? 

3.  What  are  the  "  lights ""  in  an  animal  ? 

4.  How  is  respiration  affected  by  a  stooping  posture  ? 

5.  In  what  part  of  the  lungs  is  the  best  air  ?    Where  the  worst  ? 

6.  Can  you  explain  how  respiration  affects  circulation  ? 

7.  Is  it  easy  to  determine  by  the  color  of  blood  flowing  from  a 
wound  whether  it  is  arterial  or  venous  ?     Why  ? 

8.  Of  what  advantage  is  it  that  the  cartilages  of  the  windpipe  are 
C-shaped  and  not  complete  rings  ? 

9.  How  is  it  that  in  respiration  5  per  cent  of  the  oxygen  disappears 
while  only  4  per  cent  of  carbon  dioxid  appears  in  its  place  in  the  ex- 
pired breath  ?     (See  p.  102.) 


CHAPTER   VII. 
VENTILATION   AND    HEATING  — DUST  AND    BACTERIA. 

Need  of  Proper  Ventilation.  —  When  one  is  actively 
exercising  his  muscles  he  may  keep  warm  outdoors  through 
our  winter  days.  For  the  heat  of  the  body  depends  on  its 
internal  fires,  the  oxidation  of  its  tissues.  But  if  we  are 
inactive,  these  fires  burn  feebly,  and  we  need  outside  heat. 
While  air  is  free,  it  really  costs  a  good  deal  of  money  to 
have  it  properly  warmed. 

A  Lack  of  Effective  Systems  of  Ventilation.  —  Lung 
diseases  are  rare  in  the  regions  where  the  windows  and 
doors  may  be  kept  open  most  of  the  days  of  the  year.  It 
is  from  shutting  ourselves  in  so  closely  that  we  suffer. 
This  is  especially  true  where  many  people  are  housed  in  a 
comparatively  small  space,  as  in  many  public  buildings. 
But  in  our  private  dwellings,  even  when  the  owners  are 
amply  able  to  secure  the  most  sanatory  appliances,  defec- 
tive apparatus  is  often  put  in.  Any  system  that  does  not 
provide  for  a  constant  renewal  of  the  air  is  defective. 

Grates  as  Heaters  and  Ventilators.  — Grates  will  aid 
largely  in  renewing  the  air.  Although  in  themselves  they 
merely  have  provision  for  sending  radiant  heat  out  into  the 
room  and  much  air  up  the  chimney,  yet,  without  any 
special  provision  for  inlet  of  air  to  the  room,  they  draw  air 
in  through  every  crack  and  crevice.  It  would  probably  be 
very  much  better  to  have  special  ducts  for  the  admission 

114 


VENTILATION  AND  HEATING.  11$ 

of  air,  which  is  suitably  warmed  while  on  its  way  into  the 
room,  and  to  make  the  doors  shut  snugly,  and  to  have 
double  windows,  as  then  both  the  admission  of  fresh  air 
and  the  regulation  of  heat  will  be  better  secured.  But 
it  is  a  serious  question  whether,  with  all  our  modern  ap- 
pliances, conveniences,  and  luxuries,  we  have  better  air 
in  our  houses,  and  take  cold  less  frequently,  than  our 
ancestors  who  depended  more  on  the  fireplace,  even  if 
they  did  "  roast  on  one  side  while  they  froze  on  the  other." 
Fireplaces  are  expensive  as  mere  heaters,  but  they  are 
excellent  ventilators. 

Ventilating  Flues  around  a  Smoke  Flue.  —  If  small 
ventilating  flues  could  be  built  around  the  flue  of  the  main 
heating  apparatus,  and  connected  with  the  various  rooms 
of  the  house,  air  could  be  drawn  from  these  rooms  by 
ascending  currents  created  by  the  heat  of  the  central  smoke 
flue.  Such  flues  surrounding  smoke  flues,  would  have  the 
added  advantage  of  protecting  the  house  from  fire  through 
the  too  common  "  defective  flue." 

The  General  Principles  of  Ventilation.  — Of  the  forces 
that  operate  to  renew  the  air  two  are  natural,  diffusion 
and  the  wind ;  and  two  are  artificial,  warm  air  shafts  and 
fan  systems. 

Diffusion.  —  Gases  tend  to  mix.  We  know  that  if  a 
bottle  containing  an  odorous  substance  be  opened  in 
a  room  where  there  are  no  air  currents  the  odor  tends  to 
spread  equally  through  the  room.  So  if  a  person  is  in 
one  corner  of  a  large  room,  where  there  are  no  inlets 
or  outlets,  and  no  currents,  as  he  uses  the  oxygen  immedi- 
ately around  him,  the  oxygen  farther  away  will  diffuse 
toward  him  so  that  he  will  continue  to  get  oxygen  till  the 
amount  of  oxygen  in  the  room  is  nearly  exhausted.  So, 


u6 

too,  the  gases  that  he  breathes  out  will  not  remain  confined 
to  the  space  directly  about  him,  but  will  spread  nearly 
evenly  throughout  the  room.  The  same  takes  place  in  the 
open  air,  without  wind.  So,  then,  if  the  windows  and 
doors  are  open,  the  air  of  the  room  will,  by  diffusion,  be 
renewed. 

Wind.  —  Motion  of  the  air  renews  faster  than  mere  dif- 
fusion. Strong  wind  forces  its  way  through  the  cracks 
around  windows,  and  when  windows  are  open  on  opposite 
sides  of  a  room  there  is  usually  enough  breeze  to  renew  the 
air.  But  during  the  greater  part  of  the  year  this  cannot  be 
done. 

Artificial  Renewal  of  the  Air.  —  The  renewal  of  the 
air  in  most  cases  depends  on  the  fact  that  heated  air  rises. 
Heat  expands  air.  It  is  then  lighter,  bulk  for  bulk,  than 
cooler  air.  The  heavier  surrounding  air  presses  the  lighter 
air  upward.  If  there  are  outlets  above  and  below,  the 
heavier,  colder  air  will  press  in  at  any  opening  left  below, 
and  push  the  lighter,  warmer  air  out  above. 

The  Common  Stove.  —  In  the  case  of  the  common  stove 
we  very  well  know  that  there  are  currents  of  heated  air 
rising  above  the  stove.  Children  make  whirligigs  and 
various  toys  to  place  in  these  up-currents  above  stoves. 
Air  is,  at  the  same  time,  flowing  toward  the  stove  along 
the  floor  and  lower  part  of  the  room.  Cold  air  can  usually 
be  detected  entering  around  the  windows  and  doors,  which 
presses  downward  and  toward  the  source  of  heat.  The 
stove  does  not  do  much  to  renew  'the  air  in  the  room 
except  in  this  general  way  ;  some  heated  air  escapes  at 
openings  in  the  upper  part  of  the  room,  and  some  is  passed 
out  through  the  stove,  taken  in  as  a  draft.  But  in  the 


VENTILATION  AND  HEATING.  1 1/ 

main,  the  action  of  the  heat  of  the  stove  is  to  make  a 
current  of  warm  air  up  from  the  stove,  which  current 
passes  along  the  ceiling  to  the  more  distant  corners  of  the 
room,  then  descends,  joining  the  cold  air,  and  repeating 
the  round. 

A  Stove  and  Jacket.  —  In  some  cases  a  jacket  is  placed 
around  a  stove,  and  a  duct  from  the  outer  air  connects 
with  the  lower  part  of  the  space  inside  of  the  jacket  and 
outside  of  the  stove.  Then  as  the  air  heated  by  the  stove 
rises,  fresh  air  is  drawn  in  from  outside  to  be  warmed. 
In  this  case  the  direct  heat  from  the  stove  is  shut  off  from 
the  room.  Heat  radiates  in  straight  lines.  When  one 
holds  out  his  hands  beside  a  stove  the  heat  he  receives  is 
radiant  heat.  Most  of  the  heat  from  a  grate  is  radiant 
heat.  But  in  a  jacketed  stove  the  heating  by  air  currents 
is  called  heating  by  convection. 

The  Furnace.  —  Now  a  furnace  is  practically  a  jacketed 
stove  (almost  always  placed  in  a  basement).  Furnaces 
have  this  good  feature  that  they  are  all  the  time  sending 
fresh  air  into  a  room. 

Foul-air  Shafts  and  Fans.  —  Although  in  private  dwell- 
ings heated  by  furnaces  there  is  no  special  provision  for 
the  escape  of  foul  air,  there  is  ordinarily  sufficient  renewal 
of  the  air.  But  in  public  buildings  there  should  be  escape 
flues  for  foul  air. 

Frequently  a  large  foul-air  shaft  is  built  in  some  central 
part  of  the  building,  and  a  small  stove  placed  in  it  to  create 
a  sufficient  up-current.  In  many  public  buildings  the  cur- 
rents created  by  heat  are  insufficient  to  renew  the  air 
properly.  Fans  are  used,  which  force  the  air,  properly 
heated,  into  the  room. 


Il8  rHYS/OLOGY. 

Direct  Heating.  —  In  heating  by  steam  or  hot  water,  if 
the  radiators  are  placed  in  the  room  they  give  direct  or 
radiant  heat.  This  system  is  called  direct  heating.  In 
itself  it  has  no  provision  for  renewing  the  air.  It  gives 
direct  heat,  and  produces  air  currents  within  the  room ; 
and  any  change  in  the  air  is  wholly  incidental,  from  escape 
of  heated  air  in  the  upper  parts  of  the  room  and  corre- 
sponding suction  of  outside  air  through  such  openings  as 
the  carpenters  have  left  below. 

Indirect  Heating.  —  In  indirect  heating,  coils  of  steam 
or  hot-water  pipes  are  placed  in  air  shafts  which  lead  up 
to  the  rooms  above,  and  also  have  ducts  to  the  outside. 
As  the  air  is  heated  by  the  heat  of  the  pipes  it  rises  into 
the  rooms  above,  and  fresh,  cold  air  presses  in  through  the 
ducts,  to  be,  in  turn/heated  and  sent  up.  If  there  is  at 
the  same  time  a  proper  escape  for  the  foul  air,  this  makes 
an  excellent  system. 

A  Combination  of  Direct  and  Indirect  Heating.  —  In 

many  situations  the  direct  and  indirect  may  be  advan- 
tageously combined.  Where  there  is  a  grate  in  a  room,  it 
serves  very  well  as  a  foul-air  shaft,  especially  when  there 
is  a  fire  in  the  grate.  It  is  well  to  have  the  flue  from  the 
grate  in  the  same  chimney  with  that  from  the  smoke  pipe, 
as  then  the  heat  from  the  smoke  will  cause  a  constant  up- 
draft  in  the  grate  flue,  whether  there  is  a  fire  going  in  the 
grate  or  not. 

With  a  grate,  in  private  houses,  there  is  ordinarily  no 
need  of  other  foul-air  shaft  for  any  room.  But  it  is  very 
desirable  to  have  at  least  some  "indirect"  heat,  so  that 
the  fresh  air  introduced  will  be  sufficiently  heated. 

If  the  introduction  of  air  is  thus  provided  for,  it  is  then 
safe  to  put  on  double  windows  and  make  the  cracks  around 


DUST  AND   BACTERIA.  119 

the  door  very  tight.     Without  any  special  provision  for  the 
renewal  of  the  air  these  cracks  are  the  means  of  safety. 

In  houses  heated  by  furnaces,  steam,  or  hot  water,  the 
floor  is  likely  to  be  warmer  from  the  escape  of  heat  from 
the  heater  itself,  and  from  pipes  or  air  ducts  under  the 
floor. 

Double  Windows.  — There  is  a  very  common  misunder- 
standing as  to  the  cold  felt  near  a  window  in  cold  weather. 
It  seems  that  air  is  entering ;  but  a  little  reflection  will 
show  that  even  if  the  window  were  air-tight  this  effect 
would  be  produced,  for  the  air  near  the  window  is  cooled 
by  losing  heat  to  the  outer  air.  The  air  next  to  the  win- 
dow, thus  cooled,  is  heavier,  and  falls  to  the  floor ;  and  if 
there  is  any  source  of  heat  in  the  room,  this  cold  air  will 
pass  along  the  floor  to  that  source  of  heat,  up  from  the 
heating  body  to  the  ceiling,  and  across  the  ceiling,  and  so 
on  around  again.  There  may  thus  be  currents  without 
any  appreciable  change  in  the  quality  of  the  air.  It  is 
economy  to  use  double  windows  and  prevent  the  loss  of 
heat  through  the  glass.  So  both  economy  and  comfort 
suggest  to  us  that  we  reduce  as  much  as  possible  cracks 
around  doors  and  windows,  use  double  windows,  make  ves- 
tibules at  entrances,  and  build  special  ducts  by  which  fresh 
air  may  enter,  and  heat  it  properly  on  its  way  in. 

DEAD    DUST. 

The  Air  is  washed  by  Rain  or  Snow.  —  Every  one 
will  recall  how  delightfully  refreshing  the  air  is  after  a  rain 
or  a  snowstorm.  This  is  not  due  merely  to  the  fact  that 
the  air  is  cool.  It  is  clean  because  it  has  been  washed. 
The  rain  and  snow  absorb  a  considerable  amount  of  the 
various  impure  gases  that  are  in  the  air.  But  raindrops 


120  PHYSIOLOGY. 

and  snowflakes  bring  down  with  them  many  particles  of 
dust  that  were  floating  in  the  air.  Take  some  of  the  snow 
that  has  fallen  in  a  town.  It  looks  pure  in  its  almost 
dazzling  whiteness.  But  melt  some  of  it,  and  you  will 
usually  find  a  decided  tinge  darkening  the  water,  showing 
that  as  the  flakes  sifted  down  through  the  air  they  caught 
myriads  of  particles  of  dust. 

The  Sources  of  Dust.  —  Where  soft  coal  is  used  to  any 
large  extent  it  is  one  abundant  source  of  this  dust.  In 
summer  dust  has  many  sources.  The  dust  that  blows  into 
your  face,  and  perhaps  into  your  mouth,  may  be  made  of 
dry  soil.  Take  a  dry  clod  and  drop  it ;  it  falls  quickly  to 
the  ground.  Pulverize  it  in  your  hand  before  dropping  it, 
and  considerable  of  it  floats  in  the  air  for  some  time.  Any 
substance  that  is  easily  dried. and  pulverized  may  form 
part  of  the  common  dust.  The  dust  that  you  wipe  from 
your  eye,  or  is  caught  by  the  mucus  of  the  nasal  passages, 
may,  instead  of  being  made  of  clean  soil,  be  from  the 
excreta  of  horses,  decayed  leaves,  wood,  grass,  etc.  In- 
doors we  are  constantly  making  dust  by  wearing  out  our 
clothes.  Many  of  the  tiny  particles  that  we  see  floating  in 
the  sunbeams  are  bits  of  cotton  or  woolen  fibers.  Shake 
any  garment  in  a  beam  of  light  to  see  how  much,  and  how 
easily,  dust  is  given  off.  The  worn-off  particles  of  our 
shoes,  books,  floors,  all  contribute  to  the  ever-present 
dust. 

The  Effect  of  Dust  on  the  Lungs.  —  Now,  this  dust  (so 
far  as  it  is  mere  dead,  dry  matter,  not  considering  it  as  a 
poison)  is  irritating  to  the  lungs  and  respiratory  passages. 
There  is  provision,  as  we  have  seen,  for  catching  and 
getting  rid  of  a  good  deal  of  it. 

But  still  much  is  taken   into  the   lungs.     Examination 


DUST  AND  BACTERIA.  121 

shows  that  the  lungs  have  many  black  specks  from  parti- 
cles of  carbon,  etc.,  that  have  become  lodged,  and  are  of 
no  benefit,  to  say  the  least. 

LIVE   DUST. 

Composition  of  Live  Dust.  —  Bad  as  this  dead  dust  is, 
the  injury  from  it  is  slight  compared  to  that  from  live  dust. 
We  know  that  certain  seeds  float  in  the  air,  carried  along 
by  the  wind.  But  these  are  comparatively  heavy,  and  soon 
sink  to  the  ground. 

We  all  know  pollen.  At  certain  seasons  it  forms,  in  the 
vicinity  of  cornfields,  for  instance,  a  considerable  part  of 
the  dust.  This  is  alive.  It  will  grow  if  it  falls  on  the 
right  kind  of  a  surface,  the  stigma  of  the  right  plant  at  the 
right  time.  Such  dust  will  not  grow  in  our  bodies.  We 
do  not  furnish  a  soil  in  which  it  can  grow.  It  merely  adds 
to  the  amount  of  irritating  dust. 

Puffballs  and  Molds.  —  We  have  seen  puffballs  give 
off  a  cloud  of  dust  when  they  are  crushed.  This  dust  is 
composed  of  live  spores  that  will  grow  in  suitable  places 
and  conditions.  So,  too,  from  a  patch  of  mold,  when 
brushed,  we  often  see  a  little  cloud  of  dust.  These  are  a 
few  instances  of  kinds  of  living  dust  that  simply  act  on  us 
like  so  much  dead  matter. 

Yeast.  —  If  we  set  a  tumbler  of  cider  on  a  table  in  a 
warm  room,  in  a  few  days  it  ferments.  This  is  due  to 
yeast  that  has  gotten  into  it.  Boil  the  cider  to  kill  any 
yeast  that  is  already  in  it,  and  cork  it  securely  so  that  air 
cannot  get  at  it,  and  it  will  not  ferment.  Dried  yeast 
germs  float  in  the  air,  settle  into  this  exposed  cider,  and 
cause  it  to  ferment.  Cider  is  a  good  soil  for  yeast. 


122  PHYSIOLOGY. 

Disease  Germs.  —  But  there  are  floating  in  the  air  many 
kinds  of  spores  that  may  grow  in  our  bodies.  We  know 
that  many  of  our  contagious  diseases  are  due  to  the  growth 
in  our  bodies  of  some  of  these  spores.  Our  bodies  are  a 
good  soil  for  certain  germs.  The  germs  that  cause  con- 
sumption, typhoid  fever,  Asiatic  cholera,  erysipelas,  diph- 
theria, and  some  forms  of  blood  poisoning  are  well  known. 
Microscopists  know  them  when  they  see  them  as  readily 
as  we  know  peas  from  beans.  And  it  is  proved  beyond 
all  doubt  that  these  germs  get  into  our  bodies  by  being 
breathed  in,  or  by  being  eaten  in  food,  or  in  drinking 
water,  or  by  introduction  into  the  blood  in  wounds.  We 
have  reason  to  believe  that  smallpox,  yellow  fever,  measles, 
and  scarlatina  are  caused  by  germs,  but  these  diseases  have 
not  been  studied  so  successfully. 

How  to  avoid  Germs.  —  How^can  we  avoid  or  get  rid 
of  dusts  of  these  kinds  ?  To  exterminate  any  plant,  we 
try  to  keep  the  seeds  from  ripening,  and  to  kill  all  that  do 
ripen.  Let  us  take  a  case  that,  while  not  pleasant  to  con- 
template, is  too  terribly  true  to  allow  of  being  called  an 
imagined  case. 

The  Danger  from  Consumption.  —  A  consumptive  ex- 
pectorates on  the  pavement.  In  this  sputum  are  probably 
hundreds,  if  not  thousands,  of  germs  known  as  bacilli 
(Bacillus  tuberculosis}.  They  are  alive.  Now,  so  long  as 
they  remain  on  the  pavement  they  do  no  harm.  The 
sputum  dries.  But  the  bacilli  are  not  killed  by  drying. 
With  other  dry  material  from  the  pavement  they  form 
part  of  the  common  dust.  Any  one  of  us  may  breathe 
some  of  this  kind  of  matter  any  day,  for  there  are  persons 
afflicted  with  this  dreaded  disease  in  every  community. 
Our  bodies  furnish  the  very  best  soil  for  the  germs.  We 


DUST  AND  BACTERIA. 


12$ 


Bacillus  of  "Diphtheria  (x  lOOO) 


Bacillus  of  Tuberculosis  (x  1000) 


Bacillus  of  Typhoid   Fever  (x  1200) 


Bacillus  of  Typhoid  Fever  (x  1200) 
showing  flagella 


Bacillus  (Spirillum)  of  Asiatic  Cholera  Bacillus  of  Hog  Cholera  (x  1000) 

Fig.  48.    Types  of  Bacilli,  showing  Morphologic  Characters  and  Arrangement. 


124  PHYSIOLOGY. 

do  not  need  to  go  into  the  street  to  be  exposed.  Who 
knows  what  he  brings  into  the  house  adhering  to  his 
clothing  ?  These  germs  may  be  brought  into  the  most 
cleanly  houses  in  this  way,  or  by  the  wind. 

How  to  avoid  the  Danger.  —  Now,  of  course,  all  such 
material  known  to  be  highly  dangerous  ought  to  be  de- 
stroyed. If  those  suffering  from  such  diseases  were  care- 
ful to  burn  all  such  matter,  most  of  the  seeds  of  this  disease 
would  be  killed.  Thus  in  time  we  might  stamp  out  the 
disease,  as  a  scourge  of  Canada  thistles.  But  so  long  as 
people  expectorate  upon  the  floors  and  pavements  it  will 
be  difficult  to  prevent  the  spread  of  such  germ  diseases. 

In  hospitals  such  matters  are  now  looked  after  with  the 
greatest  care,  and  in  private  houses  where  there  is  intelli- 
gence on  these  subjects.  And  it  is  encouraging  to  note 
the  awakening  of  the  public  to  the  significance  of  the  teach- 
ings of  modern  science  on  this  subject,  as  shown  by  the 
fact  that  many  of  the  railroad  and  street  car  companies 
now  prohibit  spitting  on  the  floors  of  cars,  not  merely  be- 
cause it  is  uncleanly,  but  on  the  express  ground  that  it  is  a 
means  of  spreading  infectious  diseases. 

Bacteria.  —  These  disease  germs  are  the  smallest  and 
simplest  of  living  things.  They  are  plants ;  and  while  all 
of  them  that  are  well  known  have  their  scientific  names, 
just  as  the  larger  plants  have,  they  are  all  included  in  one 
general  group  designated  as  bacteria. 

How  to  avoid  Dust.  —  We  need  to  learn  a  good  deal 
more  about  avoiding  and  destroying  dust,  and  the  things 
that  make  dust. 

Towns  and  cities  need  more  sprinkling  to  keep  the  dust 
down.  Much  more  of  the  refuse  and  street  sweepings  and 


DUST  AND  BACTERIA.  125 

cleanings  ought  to  be  burned.  The  dust  of  a  house  should 
always  be  burned,  as  we  know  not  what  germs  of  disease 
may  be  in  it.  If  we  burn  it,  we  shall  surely  not  have  to 
sweep  up  that  dust  again.  If  we  send  it  out  of  doors  it 
may  come  back,  and  we  may  have  to  handle  it  again  and 
again. 

Sweeping  and  Dusting.  —  So  far  as  possible  let  us  avoid 
things  that  make  dust.  When  we  sweep  a  carpet,  a  con- 
siderable share  of  the  dust  comes  from  the  carpet  itself, 
especially  if  the  carpet  is  old.  Curtains  and  tapestries  of 
nearly  all  sorts  not  only  hold  dust,  but  contribute  a  good 
deal  to  it.  Those  who  write  on  such  subjects  recommend 
hard  wood  floors  with  rugs  instead  of  carpets.  The  rugs 
can  be  taken  out  of  doors  and  shaken,  and  the  floors  wiped 
with  a  moist  cloth,  so  that  little  dust  is  left  floating  in  the 
air  of  the  room.  Compare  this  with  the  condition  that 
holds  after  the  ordinary  sweeping  of  a  carpeted  room  with 
the  common  broom.  The  dust  fills  the  air,  only  to  settle 
back  on  the  floor  and  furniture.  Then  comes  the  whisk 
broom,  the  so-called  dusting.  Well,  it  is  dusting !  It  fills 
the  air  once  more  with  dust.  But  do  we  get  rid  of  it? 
Wiping  off  the  dust  with  a  moist  cloth  takes  most  of  it 
away  on  the  cloth.  For  those  who  cannot  have  hard  wood 
floors  a  most  excellent  substitute  (and  in  some  respects 
better)  is  oilcloth  or  linoleum. 

Sweeping  the  Sick  Room.  -  -  The  improved  carpet 
sweepers  are  not  only  convenient,  but  sanatory.  Many  a 
well-meaning  person  will  sweep  a  carpet  in  a  sick  room 
with  an  ordinary  broom  when  the  patient  is  suffering  from 
lung  disease,  thoughtless  of  the  fact  that  a  little  dust  in 
sight,  and  perhaps  on  the  shoes,  is  of  much  less  signifi- 
cance than  dust  in  the  air  we  breathe.  No  one  likes  dust 


126  1'HYSIOLOGY. 

on  the  floor,  but  better  a  thousand  times  there  than  in  our 
lungs. 

Lung  Diseases.  —  Statistics  seem  to  show  that  one 
seventh  of  the  deaths  among  the  civilized  races  is  due  to 
lung  diseases.  The  best  authorities  are  now  agreed  that 
consumption  is  not  hereditary.  But  it  appears  that  there 
may  be  inherited  a  tendency  to  this  disease,  so  that,  if  ex- 
posed, such  persons  are  more  likely  to  contract  the  disease 
than  those  not  so  predisposed. 

Probably  anything  that  lowers  the  general  vitality  makes 
the  system  more  ready  to  succumb  to  any  of  these  con- 
tagious diseases.  We  have  all  noticed  what  a  difference 
there  is  among  individuals  in  the  readiness  with  which  they 
"  catch  "  contagious  diseases. 

Destruction  of  Germs  by  Colorless  Corpuscles.  —  It  is 

believed  by  some  physiologists  that  the  colorless  blood 
corpuscles  may  take  these  germs  of  disease  into  their  sub- 
stance, and  destroy  or  change  them  so  that  the  disease  is 
warded  off.  In  other  words,  they  may  be  compared  to  a 
cat  that  catches  and  eats  the  mice  which  invade  a  house. 

How  to  ward  off  Contagious  Diseases.  —  A  good  gen- 
eral condition  of  the  body  helps  greatly  to  ward  off  dis- 
eases of  this  nature.  A  cheerful  condition  of  mind  and 
body  should  be  cultivated.  In  times  of  widespread  con- 
tagious disease,  if  one  is  terrified  into  the  belief  that  he  is 
going  to  have  the  disease,  he  is  more  likely  to  take  it. 

Thorough  cleanliness,  plenty  of  direct  sunshine,  care  in 
diet,  and  the  keeping  of  the  body  in  good  tone,  all  these 
reduce  the  chances  of  "taking"  contagious  diseases. 

An  open-air  life,  abundant  nutritious  food,  and  freedom 
from  anxiety  are  probably  the  best  restoratives  for  incipient 
consumption. 


DUST  AND   BACTERIA.  127 

The  Bacteria  of  Putrefaction.  —  Besides  the  disease- 
producing  bacteria,  there  are  others  that  cause  decay  and 
putrefaction  of  various  kinds.  They  cause  our  richer  foods 
to  "  spoil,"  milk  to  turn  sour,  butter  to  become  rancid,  etc. 

While  these  bacteria  do  not  cause  disease  in  the  human 
body,  they  often  make  food  poisonous.  The  cases  fre- 
quently reported  of  poisoning  from  eating  ice  cream, 
cheese,  sausage,  etc.,  are  in  many  cases  due  to  bacteria  in 
them.  We  should,  in  the  first  place,  be  careful  to  get 
good,  fresh  material.  In  the  second  place,  it  should  be  so 
kept  as  to  prevent  the  introduction  and  development  of 
bacteria  in  it.  Bacteria  need  heat  for  their  growth  (as  we 
so  well  know  is  the  case  with  the  higher  plants).  They 
also  need  moisture. 

The  Preservation  of  Foods.  —  So  our  principal  modes 
of  keeping  foods  from  spoiling  are  to  keep  them  in  a  cold 
place,  or  to  dry  them.  Or  we  heat  them,  and  shut  them 
away  from  the  air,  as  in  our  various  modes  of  canning  and 
preserving  foods.  Salting  and  smoking  meats,  etc.,  preserve 
them  by  preventing  the  growth  of  bacteria.  Cold  does 
not  usually  kill  bacteria.  So  milk  that  has  been  kept  in  a 
refrigerator,  and  that  seems  sweet,  may  have  in  it  a  stock 
of  bacteria,  and  after  we  drink  the  milk  the  heat  of  our 
bodies  favors  their  development.  There  are  now  known 
ways  of  killing  the  bacteria  in  milk  and  other  liquids,  known 
as  "  sterilizing,"  that  make  us  safe  from  this  danger. 

Although  the  main  subject  of  this  chapter  is  air  and 
ventilation,  it  has  been  thought  best  to  touch  briefly  the 
subject  of  bacteria  in  food,  as  the  bacteria  are  so  widely 
disseminated  by  the  air.  One  of  the  earlier  and  still  in- 
teresting works  on  this  subject  is  Tyndall's  Floating  Matter 
of  the  Air. 


128  PHYSIOLOGY. 

But  let  us  now  turn  from  the  air  and  respiration  to 
another,  yet  closely  allied  subject. 

The  Need  of  the  Removal  of  Waste.  —  When  we 
awaken  on  a  cold  winter  morning  we  are  likely  to  find  that 
the  fire  in  our  hard  coal  stove  has  burned  low.  Not  enough 
heat  is  given  out.  What  is  the  trouble  ?  Is  it  merely  that 
more  coal  is  needed  ?  We  put  another  hod  of  coal  in  the 
magazine  (though  some  usually  remains).  Does  this  bring 
the  desired  result  ?  No.  We  open  the  draft.  Is  this  suffi- 
cient? It  is  not.  We  must  shake  down  the  grate  and 
clean  out  the  clinkers.  The  removal  of  waste  is  often 
more  necessary  than  the  addition  of  a  fresh  supply  of  ma- 
terial. It  is  often  a  more  serious  matter  to  have  the  waste 
pipe  leading  to  the  sewer  clogged  than  to  have  the  water 
supply  cut  off.  It  is  often  more  to  be  desired  that  the 
garbage  cart  take  away  decaying  matter  than  that  the 
bread  wagon  arrive.  The  demands  of  nature  for  the  ex- 
pulsion of  excreta  are  imperative,  while  we  can  withstand 
the  cravings  of  hunger  for  a  while.  So  we  shall  turn  our 
attention  for  the  present  to  the  immediate  demand  for  the 
removal  of  wastes,  and  later  consider  the  equally  impor- 
tant, but  less  importunate,  question  of  supply  and  renewal. 

READING. — (i)  Bacteria,  (2)  Dust  and  Its  Dangers, 
(3)  Drinking  Water  and  Ice  Supplies,  Prudden ;  Ventila- 
tion and  Warming  of  School  Buildings,  Morrison;  Sanitary 
Conditions  of  ScJioolJionses,  Lincoln  (American  Public 
Health  Association);  Disinfection,  Sternberg  (American 
Public  Health  Association) ;  Micro-Organisms  and  Disease, 
Klein ;  The  Wilderness  Cure,  Marc  Cook. 


Summary. —  i.    Lung  diseases  usually  accompany  close  confine- 
ment, but  are  rare  with  those  living  in  the  open  air. 


DUST  AND  BACTERIA.  129 

2.  Air  in  rooms  needs  constant  renewal. 

3.  Grates  are  good  ventilators,  but  not  economical  heaters.    Grates 
heat  very  unevenly. 

4.  Stoves  are  economical  heaters,  but  poor  ventilators.     Stove  heat 
is  also  very  uneven. 

5.  All  crowded  rooms,  as  schoolrooms  and  churches,  need  special 
inlets  for  fresh  air  and  outlets  for  foul  air. 

6.  The  most  common  means  of  withdrawing  the  air  is  by  foul-air 
shafts.     Heat  is  the  force  relied  on,  but  the  removal  of  foul  air  is  usually 
inadequate,  on  account  of  the  slowness  of  the  current  or  the  narrowness 
of  the  outlet,  or  both  combined. 

7.  Fans  are  much  more  certain  to  be  effectual. 

8.  Steam  and  hot  water  may  heat  directly  (by  radiation)  or  indi- 
rectly (placed  in  flues).     A  combination  of  direct  and  indirect  heating 
favors  economy  and  efficiency. 

9.  Dust  as  mere  dry  dead  matter  is  irritating. 

10.  Disease  germs  may  form  part  of  the  dust  of  the  air. 

1 1 .  Most  of  our  contagious  diseases  are  known  to  be  due  to  bacteria. 

12.  Burning  is  the  surest  method  of  destroying  germs. 

13.  Carpets,  tapestries,  and  cloth-upholstered  furniture  add  largely 
to  the  dust  in  houses. 

14.  Putrefaction  is  caused  by  bacteria. 

15.  Preservation  of  food  depends  on  destroying,  or  excluding,  or 
retarding  the  growth  of  the  bacteria  of  putrefaction . 

Questions.  —  i .    How  can  we  renew  the  air  of  a  room  without  having 
unpleasant  drafts  ? 

2.  Should  bedroom  windows  be  open  at  night?     Is  night  air  bad? 

3.  What  dangers  in  the  use  of  hard  coal? 

4.  Should  there  be  a  damper  in  the  smoke  pipe  of  a  hard  coal 
stove? 

5.  What  do  miners  mean  by  "  choke  damp  "  ? 

6.  What  is  hay  fever?     Asthma?     Bronchitis?     Pneumonia? 

7.  Compare  stove  and  furnace  heating. 

8.  Compare  heating  by  steam  and  by  hot  water. 

9.  Is  the  air  in  the  mountains  or  on  the  seashore  better  than  else- 
where ? 

10.    What  regions  are  recommended  for  consumptives ?     Why? 


CHAPTER   VIII. 


EXCRETION. 


Sweat  Pore 


Epi- 
dermis 

Papilla- 


THE  SKIN  AND   ITS   FUNCTIONS. 

The  Skin  throws  off  Perspiration. — The  energies  of 
the  body  —  heat  and  motion  —  are  produced  by  the  oxida- 
tion in  its  tissues. 
During  this  process 
waste  products  are 
formed,  which  if 
retained  in  the 
body  would  cause 
very  injurious 
effects. 

How  does  the 
body  get  rid  of 
these  substances  ? 
We  have  learned 
that  the  lungs 
throw  off  carbon 
dioxid,  water,  and 
certain  putrescible 
organic  matter. 
The  skin  is  constantly  throwing  off  wastes,  collectively 
called  sweat,  or  perspiration. 

The  Structure  of  the  Skin.  —  The  skin  has  two  layers, 
the  inner,  or  dermis,  and  the  outer,  or  epidermis.  A 
bruise  often  loosens  or  breaks  off  a  piece  of  the  epidermis, 

130 


Dermis 


Sweat 
Gland 


Blood 
Tube 


Bulb 


Fig.  49.    Vertical  Section  of  the  Skin. 


EXCRETION  131 

but  seldom  removes  the  dermis.  The  epidermis  is  thick 
over  the  palms  of  the  han<jls  and  soles  of  the  feet ;  else- 
where it  is  thin.  Not  often  seeing  the  whole  thickness  of 
the  skin,  we  do  not  easily  obtain  an  idea  of  its  real  thick- 
ness. The  skin  constitutes  about  one-fifteenth  of  the 
body's  weight,  and  if  tanned  makes  a  moderately  firm  and 
thick  leather  very  much  resembling  the  pigskin  used  for 
covering  footballs,  striking  bags,  etc. 

Mouth  of  Sweat  Duct 


Horny  Epider- 
mis 


Soft  Layer 


Papilla 


Dermis 

\  M 
Vein         Artery 

,Fig.  50.     Section  of  Epidermis,  showing  Papilla.     (Highly  magnified.) 

The  Epidermis.  —  The  epidermis  consists  of  many 
layers  of  cells  packed  closely  together.  The  deepest  cells 
may  be  compared  to  grapes  with  their  cell  walls  plumply 


132 

filled  out  by  the  liquids  of  the  cell.  Suppose,  for  the 
inner  layer,  grapes  set  on  end,  and  so  closely  packed 
together  as  to  press  each  other  into  elongated  prisms. 
Then  layers  less  closely  pressed,  more  nearly  spherical ; 
then  layers  of  cells  with  less  liquid  in  them,  and  somewhat 
shrunken,  like  raisins;  then  still  dryer  cells,  flattened 
parallel  with  the  surface  of  the  skin  ;  and  last,  in  the  outer 
part,  layers  of  cell  walls,  dry  and  empty,  pressed  flat  like 
empty  grapeskins.  The  flat  cell  walls  come  off  in  flakes 
(called  dandruff  from  the  scalp)  from  all  the  surface  of 
the  skin,  and  new  cells  are  continually  formed  in  the 
deeper  layers. 

The  Color  of  the  Skin.— The  pigment,  which  gives 
color  to  the  skin,  lies  in  the  deeper  layers  of  the  epidermis. 
In  albinos  this  is  wanting;  in  persons  with  a  fair  skin  it 
is  small  in  amount,  in  dark  skins  more  abundant.  Where 
the  pigment  is  irregularly  scattered  it  causes  freckles,  etc. 

A  Blister.  — A  blister  is  caused  by  separating  the  outer, 
harder  layer  of  the  epidermis  from  the  inner,  softer,  darker 
layer  of  the  epidermis,  as  shown  at  B  in  Fig.  49.  Serum, 
or  blood,  fills  the  space  between  the  separated  layers. 

The  Dermis.  —  The  dermis  consists  chiefly  of  tough 
interlacing  fibers.  Hence  the  strength  and  durability  of 
leather,  which  is  the  dermis  preserved  and  prepared.  The 
epidermis  is  usually  removed  in  tanning.  The  dermis  is 
richly  supplied  with  blood  capillaries  and  lymph  capillaries, 
but  the  epidermis  has  neither. 

Papillae. — The  outer  surface  of  the  dermis  has  numer- 
ous conical  elevations.  Over  most  of  the  skin  there  is  no 
evidence  of  these  papillae,  as  the  epidermis  envelops  them. 
But  on  the  palm  and  sole  the  papillae  are  in  rows,  and 
these  rows  are  indicated  by  the  fine  ridges. 


EXCRETION. 


133 


Hairs  and  Nails. — Hairs  and  nails  are  outgrowths  of 
the  epidermis.  Their  deeper  parts  are  embedded  in  the 
dermis,  through  which,  from  the  blood,  they  derive  their 
nourishment.  Like  the  epidermis,  they  are  dead  in  the 
outermost  part,  and  are  supplied  by  growth  from  beneath. 

Examination  of  the  Skin  with  a  Lens.  —  Place  a  linen  tester,  or 
good  pocket  lens,  on  the  palm  of  the  hand,  and  note  the  openings  of 
the  ducts  of  the  sweat  glands,  or  sweat  pores.  Count  the  pores  within 
the  square  shown.  Measure  this  square,  and  then  estimate  the  number 
of  sweat  glands  to  a  square  inch  of  the  palm. 

Epithelium  or  Epidermis 


Compound  Glands 
Fig.  51.     Evolution  of  Glands.     (After  Landois  and  Stirling.) 

The  Sweat  Glands.  —  The  sweat  glands  are  minute 
tubes  whose  inner  ends  are  closed,  and  whose  outer  ends 
open  upon  the  surface  of  the  skin.  The  tube  going 
inward  pursues  a  corkscrew-like  course  through  the  epi- 
dermis, then  becomes  straighter,  and,  having  passed 


134  PHYSIOLOGY. 

through  the  dermis,  is  coiled  up  in  a  ball  in  the  connective 
tissue  lying  just  underneath  the  inner  skin.  The  cells 
forming  the  walls  of  the  coiled  part  differ  from  those  of 
the  duct,  or  straighter  part  of  the  tube.  As  the  blood 
flows  around  the  coil  it  gives  off  lymph,  and  from  the 
lymph  the  cells  of  the  gland  take  certain  waste  matters, 
which  are  passed  out  to  the  surface  of  the  skin.  There  is 
also  some  muscular  tissue  around  the  walls  of  the  gland. 

Model  of  a  Sweat  Gland.  —  Take  a  small  rubber  tube  a  foot  long ; 
close  one  end;  tie  the  half  with  the  closed  end  into  a  globular  knot; 
around  and  between  the  coils  place  a  network  of  red  cord  to  represent 
the  blood  capillaries,  as  there  is  a  rich  supply  of  these  blood  tubes 
around  the  coil. 

The  Essential  Features  of  a  Gland.  —  i .  Cells  lining 
a  cavity,  the  cells  having  the  power  of  taking  something 
from  the  blood  (or  lymph). 

2.  Blood  supply  or  lymph  supply. 

3.  A  duct  or  tube  to  pour  out  on   some   surface  the 
liquid  taken  from  the  lymph. 

4.  Nerves  to  the  cells  by  which  their  action  is  controlled. 

5.  (Probably)   Special    nerve    centers   controlling    the 
various  glands.     The  cells  of  the  glands  in  many  cases 
so  alter  the  substances  taken  from  the  blood  that  what  is 
produced  by  the  gland  differs  from  anything  found  in  the 
blood.     The  gland  may  be  said  to  manufacture  the  liquid. 

The  Relation  between  Glands  and  the  Blood 
Supply. — The  sweat  glands,  like  all  glands,  are  largely 
dependent  on  the  amount  of  blood  supply.  In  exercising, 
the  skin  is  usually  redder  from  the  greater  blood  supply, 
and  at  the  same  time  the  glands  are  more  active ;  for, 
during  exercise,  and  immediately  after  it,  there  is  more 
waste  matter  to  be  thrown  out.  But  the  activity  of  the 
gland  is  not  a  mere  filtering  process,  due  to  the  greater 


EXCRETION.  135 

blood  pressure.  There  may  be  a  cold  sweat ;  i.e.  when 
the  skin  is  pale.  Here  is  evidence  that  the  activity  of  the 
glands  is,  primarily,  due  to  the  nerve  impulses  from  some 
nerve  center  to  the  gland  cells. 

Sweat  Glands  are  Simple  and  Excretory.  —  The  sweat 
glands  rid  the  body  of  certain  waste  matters  that  can  no 
longer  be  used.  They  are  excretory  glands.  In  structure 
they  are  simple  glands. 

Distribution  of  Sweat  Glands.  —  The  sweat  glands  are 
thickly  distributed  over  the  whole  surface  of  the  body, 
but  are  especially  numerous  and  large  on  the  palms  of  the 
hands  and  the  soles  of  the  feet.  In  the  armpits  the  glands 
are  very  large. 

The  Oil  Glands. — The  oil  glands  of  the  skin  are  dis- 
tributed over  all  the  surface  except  the  palms  of  the  hands 
and  soles  of  the  feet.  The  oily  matter  is  usually  poured 
out  around  the  hairs  as  they  emerge  from  the  skin.  It 
serves  to  oil  the  hair  and  the  skin,  and  keep  them  from 
becoming  too  dry. 

Composition  of  Sweat.  —  Sweat  is  mostly  water;  about 
one  per  cent  is  solid  matter,  including  salt  and  certain 
matters  which,  like  the  organic  waste  matter  from  the 
lungs,  easily  putrefy,  and  some  oily  matter  from  the  oil 
glands  of  the  skin. 

Experiment  to  show  Insensible  Perspiration.  — Thrust  the  hand 
into  a  glass  jar,  preferably  a  jar  that  has  been  in  a  cool  place.  Note 
the  moisture  that  soon  gathers  on  the  inside  of  the  jar  from  the  insen- 
sible sweat  of  the  hand.  A  common  fruit  jar  will  do  for  a  small  hand, 
but  a  candy  jar  is  better,  having  a  larger  mouth  and  clear  glass. 

Kinds  of  Perspiration.  —  Ordinarily  the  sweat  is  evapo- 
rated as  fast  as  it  is  poured  out ;  in  distinction  from  this 
insensible^  perspiration,  there  is  the  so-called  sensible  per- 


136  PHYSIOLOGY. 

spiration  —  when  it  accumulates  enough  to  be  perceptible. 
These  are  not  two  distinct  kinds  of  sweat,  but  it  is  con- 
venient to  distinguish  between  the  perceptible  and  the 
imperceptible.  Sweat  varies  greatly  in  its  wateriness,  and 
hence  in  the  relative  amount  of  solid  matter  contained. 

The  Amount  of  Perspiration. — There  is  about  one 
quart  in  twenty-four  hours.  It  varies  with:  — 

1.  Temperature,  dryness,  and  rate  of  renewal  of  air. 

2.  Condition  of  the  blood;  e.g.  if  watery  from  drinking 
much  water. 

3.  Muscular  exercise. 

4.  Certain    drugs  —  some    exciting    perspiration,    e.g. 
camphor ;   others  diminishing  it,   e.g.  belladonna. 

5.  The  nerves  exercise  great  influence  on  the  activity  of 
the  cells  of  the  gland. 

The  Functions  of  the  Skin. 

1 .  Protective. 

2.  Excretory. 

3.  Absorptive. 

4.  Sensory  —  organ  of  touch. 

5.  Heat-regulating. 

Next  to  its  excretion,  the  heat  regulation  by  the  skin  is 
the  most  important  for  our  present  consideration. 

Regulation  of  the  Temperature  of  the  Body  by  the 
Skin.  —  It  is  a  striking  fact  that,  except  in  disease,  the 
temperature  of  the  body  varies  only  a  little  from  98.5°  F. 
in  summer  and  winter,  during  exercise  and  rest.  The  rate 
of  heat  production  varies  greatly.  The  rate  of  giving  off 
heat  must  therefore  vary  accordingly. 

The  Body  gives  off  Heat.  —  In  considering  the  regula- 
tion of  the  body's  temperature,  we  must  bear  in  mind  that 
the  body  is  surrounded  by  air  almost  always  considerably 


EXCRETION.  137 

cooler  than  itself.  The  body  is,  therefore,  almost  always 
giving  off  heat.  Our  clothes  do  not  warm  us  :  we  warm 
them,  and  they  keep  us  from  warming  the  air  too  fast ; 
i.e.  keep  us  from  losing  too  much  heat.  Indoor  heat  in 
winter  in  the  cooler  parts  of  the  United  States  is  kept 
at  about  70°  F.  by  artificial  heat.  This  air  does  not  warm 
us.  We,  being  about  30°  F.  warmer,  are  warming  it. 

Ways  of  Giving  off  Heat.  — The  skin  gives  off  heat  by— 

1.  Radiation:  heat  is  given  off  in  every  direction. 

2.  Conduction:  whatever  we  touch  that  is  cooler  than 
our  bodies  is  warmed.     We  warm  chairs,  clothing,  etc. 

3.  Convection  :  the  air  in  contact  with  the  skin  is  warmed 
and  rises.    Our  bodily  heat  is  thus  carried  off  by  convection. 

4.  Evaporation :  the  evaporation  of  the  sweat  is  a  much 
more  important  factor  in  heat  regulation.     Any  liquid,  in 
evaporating,  absorbs  heat.     The  cooling  effect  of  alcohol 
or  ether  on  the  skin  is  due  to  the  fact  that  heat  is  taken 
from  the  body  in  converting  the  liquid  into  a  gas. 

Experiments  in  Evaporation.  —  Let  the  teacher,  with  a  medicine 
dropper,  place  a  drop  of  alcohol,  ether,  or  cologne  on  the  back  of  the 
hand  of  each  pupil.  Notice  two  facts:  (i)  It  produces  a  cooling 
effect.  (2)  The  liquid  soon  disappears.  To  prove  that  it  is  not 
merely  that  the  liquid  is  cool,  try  the  following :  Tie  a  piece  of  cheese 
cloth  around  the  bulb  of  a  thermometer ;  dip  the  bulb  into  a  dish  of 
alcohol  or  ether,  and  note  its  temperature  (if  these  are  not  at  hand, 
gasoline  serves  very  well,  or  even  water,  though  the  evaporation  is 
slower)  ;  then  lift  the  bulb  out  of  the  liquid,  and  note  any  change  in 
temperature.  The  evaporation  of  the  liquid  takes  heat  from  the  bulb, 
and  causes  the  thermometer  to  register  a  lower  temperature.  We 
sponge  the  face  and  hands  of  a  feverish  patient  to  reduce  the  amount  of 
heat.  We  sprinkle  the  floor  in  hot  weather,  and,  by  the  absorption 
of  heat  in  evaporating  the  water,  cool  the  air  of  the  room. 

Heat  and  Exercise. — When  we  exercise,  we  produce 
more  heat :  we  sweat  more ;  more  heat  is  taken  from  the 


PHYSIOLOGY. 

body  to  evaporate  this  sweat.  If  we  are  not  exercising, 
and  are  in  cooler  air,  we  sweat  less,  and  less  heat  is  given 
off.  So  the  temperature  of  the  body  is  kept  uniform. 

This  should  also  be  observed  :  When  we  exercise,  more 
blood  is  in  the  skin,  and  more  heat  is  given  off  in  the 
other  ways  mentioned ;  when  we  exercise  less,  the  skin, 
especially  in  a  cool  air,  becomes  paler;  i.e.  has  less 
blood  in  it,  and  heat  is  economized. 

Distribution  of  Heat  in  the  Body.  —  If  more  heat  is 
produced  in  one  part  of  the  body  than  in  the  others,  the 
circulation  of  the  blood  tends  to  equalize  the  temperatures 
of  the  different  parts.  So,  too,  if  one  part  is  cooled,  — 
that  is,  is  losing  heat  faster  than  the  others,  —  the  blood 
brings  heat  from  other  organs  to  that  part. 

For  instance,  if  one  holds  his  hands  in  the  snow,  or  puts 
a  piece  of  ice  on  his  wrist,  the  whole  blood  stream  is 
affected.  So  if  the  hands  and  the  feet  are  exposed  to  the 
cold,  it  may  do  little  good  to  have  the  rest  of  the  body 
covered.  A  pair  of  wristers  and  a  pair  of  leggings  may 
often  add  more  to  one's  comfort  than  a  heavy  overcoat. 

Regulation  of  Bodily  Temperature  by  Food  and 
Clothing.  —  When  subject  to  the  influence  of  cold  we  eat 
more  ;  we  choose  more  heat-producing  foods,  as  fatty  food- 
stuffs ;  we  take  more  vigorous  exercise ;  we  put  on  more 
clothing,  and  especially  of  the  non-conducting  kinds,  — 
woolens.  In  warmer  weather  we  eat  less  fatty  matter, 
wear  less  clothing,  and  are  less  disposed  to  exercise 
actively  ;  we  fan  ourselves  to  help  get  rid  of  heat ;  we 
take  ices  and  cold  drinks.  For  most  persons  it  seems 
better  to  wear  woolen  most  of  the  time,  as  even  in  summer 
we  are  subject  to  sudden  changes  in  the  air,  and  with  such 
covering  one  is  less  likely  to  take  cold. 


EXCRETION.  1 39 

The  Effect  of  Wet  Clothing. —  In  getting  the  clothing 
wet,  the  greater  loss  of  heat  is  not  from  the  coolness  of 
the  water,  but  the  loss  of  heat  in  evaporating  the  water 
from  the  clothing  ;  and  this  goes  on  for  a  long  time.  Of 
course  it  is  desirable  to  put  on  dry  clothing  as  soon  as 
possible  ;  but  a  person  in  good  health  is  not  likely  to  take 
cold,  except  in  very  cold  weather,  if  he  continues  active 
exercise  till  he  can  change  the  wet  garments  for  dry  ones. 
Children  do  not  often  take  cold  from  wading  in  water  so 
long  as  they  are  barefooted ;  but  if  the  shops  and  stock- 
ings are  wet,  they  are  likely  to  take  cold. 

Sunshine.  —  For  good  health  we  need  sunshine.  We 
have  sunlight  indoors,  but  so  do  many  plants  that  drag 
out  a  sickly  existence.  We  need  direct  sunlight  (not  too 
hot),  and  many  an  invalid  has  been  cured  by  sunbaths. 
Part  of  the  beneficial  effects  of  sea  bathing  is  due  to  sun- 
shine. It  is  a  good  thing  that  it  is  now  the  fashion  to  take 
a  vacation  and  become  well  tanned.  One  of  the  benefits  of 
the  resorts  of  Colorado  (in  addition  to  the  climate's  mild- 
ness) is  that  there  are  very  few  cloudy  days  during  the  year. 

THE  KIDNEYS" 

The  Work  of  the  Kidneys.  —  One  important  part  of  the 
work  of  the  lungs,  as  we  have  seen,  is  to  throw  out  carbon 
dioxid.  The  skin  also  throws  off  certain  wastes.  The  kid- 
neys have  the  special  task  of  excreting  a  waste  product  of 
the  body  called  urea.  Urea  is  the  nitrogen-containing  waste. 

The  Parts  of  the  Kidney.  —  The  kidneys  are  attached  to  the  dorsal 
wall  of  the  abdominal  cavity.  The  depression  in  the  kidney  correspond- 
ing to  the  stem  scar  on  a  bean  is  called  the  hilum.  From  the  hilum 
issues  a  white  tube,  the  ureter,  which  conveys  the  urine  to  the  bladder. 

The  Blood  Supply  of  the  Kidneys.  —  Entering  the  kidney  along- 
side the  ureter  is  the  renal  artery,  a  branch  of  the  aorta,  and  from  near 


140 


PHYSIOLOGY. 


the  same  point  the  renal  vein  returns  the  blood  from  the  kidneys,  and 
pours  it  into  the  postcaval  vein.  Through  the  kidneys  is  pouring  a 
continuous  stream  of  blood,  varying  in  amount  at  different  times  and 
in  different  conditions.  The  kidney  receives  a  very  large  amount  of 
blood  for  its  size,  as  compared  with  other  organs.  The  flow  to  it  is 
made  easy  by  the  fact  that  the  renal  arteries  are  relatively  wide  and 
short,  and  take  the  blood  directly  from  the  main  current  of  the  aorta. 
The  blood  leaving  the  kidney,  especially  when  in  full  activity,  is  still 
bright  red ;  it  is  probably  the  purest  blood  in  the  body. 

Urine.  —  From  the  kidney,  through  the  ureter,  urine  is  continually 
passing  to  the  bladder.  Urine  is  mostly  water  containing  urea,  salt,  and 
various  other  substances  in  small  amounts.  Urea  is  a  waste  matter 
brought  in  the  blood.  If  the  kidneys  are  stopped  in  their  action,  urea 
accumulates  in  the  blood,  and  death  soon  results  ;  to  just  the  degree  that 
the  kidneys  fail  in  performing  their  duty,  just  so  far  must  the  body  suffer. 

Microscopic  Structure  of  the  Kidney.  —  If  microscopic  sections  of 
the  kidney  are  at  hand  they  should  be  examined ;  but  the  kidney  is  so 

complicated  in  structure  that  a 

Urinary  Cone  diagram  is  needed  in  connection 

with   the   sections   and  the  de- 
scriptions.    The  unit   of  struc- 
ture in  the  kidney  is  a  tube  which 
takes     material    from    adjacent 
blood  capillaries.     The  relation 
of  the  capillaries  to  the  tube  is 
peculiar.     The  inner  end  of  the 
tube  is  enlarged  into  a  ball ;  this 
ball  is  deeply  depressed  opposite 
the  point  where  the  tube  leaves 
it.     Into  this    depres- 
sion is  fitted  a  globu- 
lar tuft  of  capillaries. 
The  arrangement  may 
be   illustrated   by   the 
common  toy  known  as  the  "  cup 
and   ball."     The   handle  of  the 
cup  should  be  hollow  to  repre- 
sent the  tube ;  the  cup  should  be  double  walled,  the  space  between 
the  inner  and  outer  layers  continuous  with  the  hollow  of  the  handle. 


Cavity  of — 
Kidney 


Renal 
Vein 


Fig.  52. 


U  rete  r 
Cross  Section  of  Kidney. 


EXCRETION. 


Instead  of  a  solid  ball  held  by  one  string,  there  should  be  a  yarn  ball 
with  two  large  strings  attached  to  one  side,  one  representing  the  artery, 
the  other  the  vein  ;  the  yarn  ball  represents  the  dense  cluster  of  capil- 
laries. 

Another  Illustration.  —A  still  better  illustration  of  the  urinary  tube 
and  capsule  may  be  made  thus  :  Take  a  thistle  tube  (used  in  the  chem- 
ical laboratory),  let  down  into  its  bulb  a  rubber  balloon  or  bag  of  sheet 
rubber  or  cloth,  fastening  the  margin  around  the  rim  of  the  bulb ;  put 
a  little  ball  of  red  yarn  in  the  depression  of  the  bag  hanging  in  the 
bulb  ;  have  two  ends  of  the  yarn  projecting  to  represent  the  artery 
entering  and  the  vein  leaving  the  capsule.  The  vein,  soon  after  it 
emerges,  breaks  up  into  another  set  of  capillaries  which  extend  around 
the  tube.  A  number  of  these  primary  tubes  unite,  and  many  of  the 
common  ducts  open  at  the  apex  of  each  of  the  urinary  pyramids, 
emptying  their  secretion  into  the  cavity  of  the  kidney.  As  the  blood 
flows  through  the  tuft  of  capillaries  in  the  capsule  at  the  end  of  the 
tube,  a  large  amount  of  water, 
together  with  salt  and  some 
other  substances,  pass  through 
the  thin  partition  into  the 
cavity  of  the  capsule,  and 
thence  down  the  tube.  The 
walls  of  the  tube  are  thicker 
than,  and  its  cells  are  different 
from,  those  of  the  capsule. 
These  cells  take  the  urea  and 
some  other  substances 
from  the  blood,  and 
pass  them  into  the  tube 
to  join  the  more  watery 
material  from  the  capsule. 


Artery J 


—   Vein 


Urinary  Tul 
Fig.  53.  Urinary  Cone  Enlarged.  (Diagram.) 


Comparison  of  the  Skin 
and   the    Kidneys.  —  The 

kidneys,  then,  are  not  very 

different    from     the     skin. 

Imagine  a  piece  of  skin  rolled  up  with  the  outer  surface  of 

the  skin  turned  inward.     Its  glands  then  would  pour  their 


142  PHYSIOLOGY. 

secretion  into  a  cavity  where  it  might  accumulate,  instead 
of  evaporating  as^fast  as  it  is  poured  out.  Of  course  the 
kidneys  have  a  somewhat  different  work  from  the  skin, 
but  in  its  general  plan  of  working  we  might  say  they 
are  skin  turned  outside  in.  The  kidney  unit  (the  tubular 
gland)  has  branches ;  i.e.  is  compound.  The  kidney  is  a 
compound  gland  of  excretion,  internal  in  position.  Both 
skin  and  kidneys  excrete  a  large  amount  of  water,  with 
salt  and  some  other  matter  in  common. 

Relation  between  the  Work  of  the  Kidneys  and  that 
of  Skin. — There  is  a  very  immediate  relation  between 
the  work  of  the  kidneys  and  that  of  the  skin.  In  warm 
weather,  and  when  exercising  actively,  we  perspire  freely, 
and  the  amount  of  urine  is  reduced ;  when  we  exercise 
less,  and  especially  in  cold  weather,  we  perspire  less,  and 
the  urine  is  more  abundant.  Cold  drives  the  blood  from 
the  surface.  Consequently  more  blood  goes  to  the  kidneys 
(as  well  as  to  the  other  internal  organs),  and  they  throw 
off  much  more  water,  though  probably  little  if  any  more 
urea.  The  average  daily  amount  of  urine  is  about  three 
pints.  The  quantity  is  increased  by  high  blood  pressure, 
copious  drinking,  by  cold  air  (driving  the  blood  from,  the 
skin),  nitrogenous  food,  certain  drugs,  etc.  It  is  dimin- 
ished by  a  lowered  blood  pressure,  profuse  sweating, 
diarrhea,  non-nitrogenous  food,  and  some  diseases  of  the 
kidneys,  etc. 

What  is  the  effect  of  all  the  processes  thus  far  studied 
,on  the  weight  of  the  body  ? 

READING.  —  The  Skin  and  Its  Troubles,  D.  Appleton 
&  Co.  

Summary.  —  i .  The  skin  throws  off  sweat,  which  is  water  contain- 
ing waste  matter. 


EXCRETION.  143 

2.  The  tubular  sweat  glands  take  the  wastes  from  the  lymph  which 
soaks  out  through  the  walls  of  the  capillaries  in  the  skin. 

3.  The  activity  of  the  glands  is  under  control  of  nerves  and  nerve 
centers,  as  is  also  the  supply  of  blood  to  the  skin. 

4.  The  amount  of  sweat  depends  on  temperature,  exercise,  amount 
of  liquid  food  taken,  drugs,  etc. 

5.  The  temperature  of  the  body  is  regulated  chiefly  by  the  evapora- 
tion of  sweat. 

6.  In  cold  weather  we  eat  more  of '  heat-producing  foods,  such  as 
fats. 

7.  The  kidneys  excrete  urea,  a  nitrogen-containing  waste. 

8.  There  is  an  intimate  relation  between  the  workings  of  the  lungs, 
skin,  and  kidneys. 

Questions.  —  i.    Does  cutting  hair  make  it  grow  faster  ? 

2.  Do  cows,  dogs,  and  cats  sweat  ? 

3.  Why  is  thirst  relieved  by  immersion,  even  in  salt  water  ? 

4.  Why  should  clothing  worn  during  the  day  be  removed  at  night  ? 

5.  How  does  the  body  lose  heat,  except  by  the  skin  ? 

6.  Why  should  the  blood  still  be  red  after  passing  through  the 
kidney  ? 

7.  What  is  "skin  grafting"  ? 

8.  Why  is  it  considered  a  good  sign  when  the  skin  becomes  moist 
during  a  fever  ? 

9.  Can  food,  medicine,  or  poison  be  absorbed  through  the  skin  ? 


CHAPTER   IX. 
FOODS  AND  COOKING. 

Necessity  of  Food.  —  Thus  far  we  have  been  studying 
processes  by  which  the  body's  weight  is  reduced.  We 
have  studied  the.  oxidation  in  the  tissues  and  the  removal 
of  the  wastes.  Unless  the  tissues  receive  a  corresponding 
supply  the  heat  and  energy  of  the  body  cannot  long  be 
maintained. 

Food  Defined.  —  All  substances  that  go  to  make  up  the 
tissues  or  produce  energy  are  foods.  Certain  substances 
that  do  not  become  part  of  any  tissues,  nor  in  themselves 
produce  energy,- are  useful  in  aiding  the  processes  going 
on  in  the  body.  These  may  be  called  accessory  foods,  e.g. 
condiments  ;  some  accessory  foods,  such  as  coffee,  seem  to 
retard  the  waste  of  tissues. 

Foods  and  Foodstuffs.  —  Most  of  our  articles  of  food 
consist  of  two  or  more  different  kinds  of  materials.  For 
instance,  milk  consists  (i)  chiefly  of  water;  in  this  are  (2) 
the  substance  that  makes  cheese  (casein);  (3)  cream,  from 
which  we  get  butter  (fat) ;  (4)  sugar,  which  gives  milk  a 
sweet  taste;  (5)  salts,  such  as  common  salt,  lime  salts, 
etc.  These  different  materials  are  foodstuffs.  We  have 
many  kinds  of  foods,  but  few  foodstuffs,  which  we  find 
occurring  over  and  over  again,  in  various  forms,  in  the 
numerous  things  we  eat. 

144 


FOODS.  145 

Kinds  of  Foodstuffs. 

1.  Proteids  (exatnple,  casein).  4.    Water. 

2.  Fats.  5.    Salts. 

3.  Carbohydrates  (example,  sugar).  6.    Oxygen. 
Oxygen  is  by  some  authors  called  a  food,  but  it  is  more 

convenient  to  treat  of  it  elsewhere. 

The  Proteids. — The  chief  substance  in  the  white  of  an 
egg  is  albumen,  a  typical  proteid.  Of  the  many  proteids 
some  of  the  more  commonly  known  are  casein  (the  curd  of 
milk),  gluten  (in.  grains),  legumin  (in  peas  and  beans), 
fibrin  (in  blood),  myosin  (in  muscles).  Gelatin  (obtained 
from  connective  tissue  and  bones  by  prolonged  .boiling) 
differs  considerably  from  the  proteids  in  composition,  but 
may  be  counted  in  with  them.  It  is  less  valuable  as  a 
food  than  the  true  proteids,  although  in  certain  circum- 
stances more  desirable  from  the  fact  that  it  is  very  easily 
digested. 

Characteristics  of  Proteids.  —  The  proteids  are  — 

1.  Composed  of  carbon,  hydrogen,  oxygen,  nitrogen,  a 
little  sulphur,  and,  in  some,  traces  of  phosphorus. 

2.  Jelly-like,  and  do  not  easily  diffuse  through  animal 
membranes  (a   characteristic    to   be   kept  in  mind  when 
studying  digestion). 

3.  Coagulable  (usually)  by  heat,  acids,  alcohol,  etc. 

4.  Easily  putrefy  when  moist  and  warm. 

Importance  of  Proteids.  —  The  proteids  are  of  special 
importance  as  foods  because  the  most  active  tissues,  muscle, 
nerve,  and  gland,  and  the  most  important  liquids  of  the 
body,  e.g.  blood  and  lymph,  have  proteid  as  a  chief  con- 
stituent. Proteid  food,  therefore,  must  be  taken  to  make 
good  the  losses  of  these  tissues  during  their  oxidations. 


146  PHYSIOLOGY, 

Proteid-containing  Foods.  -  -  The  principal  proteicl- 
containing  foods  are  lean  meat,  fish,  eggs,  milk,  cheese, 
and  some  seeds  which  abound  in  the  vegetable  proteids. 

Meat.  —  Lean  meat  has  about  twenty  per  cent  of  pro- 
teid,  the  rest  being  chiefly  water.  Beef  and  mutton  are 
more  easily  digested  than  veal  and  pork.  It  is  better  to 
buy  meat  from  a  very  fat  animal  than  from  a  lean  one,  for, 
although  there  is  slightly  less  proteid  in  the  meat  from  a 
fat  animal,  this  loss  is  more  than  made  up  by  the  addition 
of  fat,  which  takes  the  place  of  water  in  the  meat  from  a 
lean  animal.  There  is  more  nourishment  in  a  round  steak 
than  in  tenderloin. 

Fish.  —  Fish,  when  fresh,  is  a  good  food.  Although, 
as  a  rule,  salted  meats  are  less  easily  digested  than  fresh, 
salted  codfish  is  a  nourishing  and  economical  food. 

Eggs.  —  Eggs  contain  considerable  proteid,  but  their 
value  as  food  has  been  overrated.  The  yolk  has  a  large 
amount  of  fat.  Although  the  egg  has  all  the  material 
needed  to  form  a  chick,  it  is  not  a  perfect  food  for  man. 

Milk.  —  Milk,  as  we  have  seen,  is  an  ideal  food  in  that 
it  contains  all  the  kinds  of  foodstuffs,  and  in  the  right  pro- 
portion for  the  young  mammal.  But  the  proportions  are 
not  right  for  the  adult.  An  adult  would  need  four  quarts 
and  a  half  daily,  and  then  he  would  not  get  enough  carbo- 
hydrates (represented  in  milk  by  the  sugar).  The  oily 
material  in  milk  is  in  the  form  of  minute  globules,  which 
can  easily  be  seen  under  the  microscope.  Each  of  these 
oil  droplets  is  supposed  to  be  surrounded  by  a  thin  en- 
velope of  albuminous  matter,  by  means  of  which  it  is 
enabled  to  remain  suspended  for  some  time  instead  of 
rising  quickly  to  the  surface.  Such  a  mixture  of  oil  in  a 


FOODS.  147 

liquid  is  called  an  emulsion.     When  cream  is  churned  the 
albuminous  covering  is  removed  and  the  butter  "gathers." 

Cheese.  —  Cheese  is  very  rich  in  proteid,  much  more  so 
than  lean  meat.  Yet,  as  it  is  rather  difficult  of  digestion, 
we  do  not  use  it  largely  as  food ;  we  regard  it  more  as  a 
luxury,  while  in  many  parts  of  Europe  it  is  largely  used  as 
food,  taking  the  place  of  meat.  It  is  a  cheap  food,  and 
might  well  be  used  more  extensively,  especially  by  laboring 
men.  When  taken  with  milk  it  is  said  to  be  more  readily 
digested. 

Vegetable  Proteids.  —  Peas  and  beans  (dried)  contain 
as  much  proteid  (legumin)  as  meat,  and  all  the  cereals 
contain  some  proteid  (gluten). 

Fats.  —  Fats  are  composed  of  carbon,  hydrogen,  and 
oxygen.  The  oxygen  is  small  in  amount,  so  these  foods 
yield  a  great  amount  of  energy  by  the  oxidation  of  their 
carbon  (forming  carbon  dioxid)  and  hydrogen  (forming 
water).  The  fats  most  used  are  animal  fats,  including 
butter.  But  some  vegetable  oils,  such  as  olive  and  cotton- 
seed oils,  are  used. 

The  Carbohydrates.  —  Starch  and  sugar  are  the  chief 
carbohydrates.  Starch  is  used  in  larger  quantity  than  any 
other  foodstuff  except  water.  Sugar  is  usually  regarded 
as  a  luxury,  yet  it  is  an  important  food.  It  is  quickly 
absorbed. 

Carbohydrate-containing  Foods.  —  The  principal  car- 
bohydrate-containing foods  are  the  grains,  vegetables,  and 
fruits. 

The  Grains.  —  The  most  important  grains  are  wheat, 
corn,  rice,  oats,  rye,  and  barley. 


148  PHYSrOLOGY. 

Wheat.  —  Wheat  furnishes  the  principal  breadstuff 
among  the  more  civilized  nations.  It  is  especially 
adapted  to  the  temperate  zones.  Taking  into  consid- 
eration its  composition,  digestibility,  and  other  charac- 
teristics, it  is  the  most  desirable  of  all  the  grains  for 
civilized  man. 

Wheat  Flour.  —  In  ordinary  white  flour  nearly  all  the 
gluten  has  been  removed  with  the  bran  or  "  middlings." 
While  wheat  or  bread  made  from  the  whole  grain  of  the 
wheat  may  support  life,  one  would  starve  if  he  attempted 
to  live  on  common  white  bread  alone.  It  is  almost  en- 
tirely starch.  In  the  "entire  wheat  flour"  it  is  claimed 
that  all  the  gluten  is  retained,  only  the  very  thin  outer 
husk  of  the  grain  being  removed.  It  does  not  make  so 
white  a  flour,  but  it  is  better  adapted  to  use  as  a  food.  If 
we  use  white  bread,  having  thrown  away  the  nitrogenous 
part  of  the  wheat,  we  need  to  take  more  proteid  from 
other  sources  than  if  we  used  the  entire  wheat  flour.  This 
is  not  economy.  And  it  is  claimed  that  the  entire  wheat 
bread  is  more  wholesome  as  well  as  more  nutritious.  The 
part  thrown  away  has  in  it  phosphates  as  well  as  the  nitrog- 
enous material.  This  flour  is  ground  fine  so  that  it  has 
not  the  coarse  particles  which  are  in  Graham  flour,  and 
which  are  a  source  of  irritation  to  the  mucous  coat  of  the 
digestive  tube  in  some  persons. 

Corn.  — Corn  is  one  of  the  most  nutritious  of  the  grains. 
Professor  W.  O.  Atwater,  one  of  the  best  authorities  in 
the  world  on  the  subject  of  foods,  says  that,  for  a  given 
amount  of  money,  more  nutriment  can  be  obtained  in  corn 
meal  than  in  any  other  food  known.  Corn  is  said  to  fur- 
nish food  to  a  larger  part  of  the  human  race  than  any 
other  grain  except  rice. 


FOODS.  149 

Rice.  —  Rice  forms  a  larger  part  of  human  food  than 
the  product  of  any  other  plant,  being  often  an  almost  ex- 
clusive diet  in  India,  China,  and  the  Malayan  islands. 
Rice  has  a  larger  proportion  of  starch,  and  less  of  fats 
and  albuminoids,  than  the  other  grains.  It  is  best  adapted 
for  the  food  of  warm  climates. 

Oats.  —  This  grain  was  first  used  as  food  for  man  by 
the  Scotch,  but  the  use  has  extended  and  become  preva- 
lent in  this  country.  In  point  of  nutrition  it  is  ranked 
higher  by  some  than  ordinary  grades  of  wheat  flour. 

Rye.  —  Rye  grows  farther  north  than  other  grains,  and  is  largely 
used  for  bread  in  Russia  and  parts  of  Germany.  It  is  a  valuable  food, 
though  less  nutritious  and  less  digestible  than  the  corresponding  prepa- 
rations of  wheat. 

Barley.  —  This  grain  has  wide  range  of  cultivation,  and,  while  in- 
ferior to  wheat,  is  considerably  used  where  other  grains  cannot  be 
raised. 

Potatoes.  —  Potatoes  contain  about  twenty  per  cent 
starch,  two  per  cent  of  proteid,  and  no  fat,  the  remainder 
being  chiefly  water,  with  some  useful  salts,  especially 
potash  salts.  In  spite  of  its  relatively  low  food  value,  the 
potato  is  our  most  useful  vegetable  on  account  of  its 
abundance,  the  ease  with  which  it  can  be  preserved,  its 
mild  flavor,  and  the  readiness  and  the  variety  of  ways 
in  which  it  can  be  cooked. 

Other  Vegetables.  —  The  chief  nutrient  in  vegetables 
is  starch,  though  in  many  the  starch  is  present  in  small 
amounts.  The  salts  and  acids  present  are  of  value,  and 
care  should  be  observed  not  to  remove  too  much  of  these 
salts  in  cooking.  The  fibrous  matter,  cellulose,  while  in- 
digestible, is  of  value  in  adding  bulk  to  the  mass  of  food 
to  be  digested.  Formerly  sailors  were  subject  to  scurvy ; 


150  PHYSIOLOGY. 

this  is  now  attributed  to  a  diet  of  fat  and  salt  meat,  to  the 
exclusion  of  fresh  vegetables,  vegetable  acids,  etc.  The 
disease  is  avoided  by  a  greater  use  of  vegetables,  lime 
juice,  etc. 

Fruits.  —  Many  of  the  fruits,  such  as  bananas  and 
apples,  have  considerable  starch  and  sugar.  But  the 
fruits  are  probably  more  useful  to  us  on  account  of  their 
flavor,  due  to  aromatic  bodies,  and  to  their  salts  and  the 
peculiar  fruit  acids. 

Water.  —  Water  constitutes  about  two  thirds  of  the 
entire  weight  of  the  body.  It  constitutes  the  bulk  of  the 
liquids  we  have  studied,  blood,  lymph,  sweat,  saliva,  bile, 
etc.  Water  is  the  solvent  and  carrier  of  all  the  material 
of  the  body.  Hence  we  need  a  large  amount  of  it ;  of 
course  we  must  remember  that  we  get  a  good  deal  of  water 
in  most  of  our  solid  foods. 

Rain  Water.  —  Water,  as  it  comes  from  the  clouds,  is 
pure.  After  enough  rain  has  fallen  to  wash  the  air,  rain 
water  is  pure,  and  if  caught  on  a  clean  roof  (especially  a 
slate  roof)  and  kept  in  a  clean  cistern,  it  is  good  drinking 
water. 

Well  Water.  —  Falling  upon  the  earth,  the  rain  water 
soaks  down  until  stopped  by  some  impervious  layer,  such 
as  clay.  This  water  is  the  supply  of  our  wells  and  springs. 
It  always  has  more  or  less  earthy  matter  in  solution,  and 
is  therefore  more  or  less  "  hard."  Unless  a  large  amount 
of  mineral  matter  or  some  special  material  is  dissolved  in 
it,  it  is,  ordinarily,  good  drinking  water.  Such  water  is 
not  pure,  in  the  strict  sense  of  the  word,  but  is  pure  for 
drinking  purposes. 


FOODS.  I  5 1 

Impurities  in  Water.  —  The  great  source  of  danger  is 
from  what  are  called  "  organic"  impurities.  Bacteria  will 
not  live  and  grow  in  pure  water.  They  must  have  some- 
thing on  which  to  feed  and  grow.  But  in  water  contain- 
ing a  large  amount  of  decaying  animal  or  vegetable  matter 
they  are  likely  to  abound.  And  the  most  dangerous 
sources  of  contamination  are  cesspools  and  sewers.  Water 
may  be  contaminated  by  such  material  and  not  have  bac- 
teria in  it,  but  is  very  likely  to  harbor  such  foes. 

Contamination  from  Cesspools.  —  The  ordinary  cess- 
pool is  a  grave  source  of  danger.  Because  the  well  may 
be  on  higher  ground  than  the  cesspool  does  not  give  as- 
surance that  the  water  may  not  be  polluted.  Often  when 
the  surface  of  the  ground  slopes  in  one  direction,  the  strata 
underneath  may  slope  in  just  the  opposite  direction,  and 
the  well  may  be  the  reservoir  into  which  the  cesspool  is 
drained. 

Good  authorities  say  that  a  cesspool  should  not  be 
allowed  within  a  hundred  feet  of  a  well. 

Abolish  the  Cesspool.  —  But  it  is  better  and  safer  to 
have  no  cesspool.  Where  a  sewer  system  is  not  to  be 
had,  it  is  better  to  allow  no  great  accumulation  of  such 
material.  A  deep  pit  in  which  a  quantity  of  semiliquid 
matter  gathers  is  not  only  a  nuisance,  but  a  source  of 
danger.  Privies  should  have  a  very  shallow  pit,  or  none, 
and  should  be  cleaned  often.  There  should  be  a  little 
dust  sprinkled  in  each  day,  and  occasionally  some  "  chlorid 
of  lime  "  or  sulphate  of  iron. 

Typhoid  Fever.  —  Typhoid  fever  is  now  known  to  be 
usually  caused  by  drinking  water.  The  dejecta  of  some 
one  who  has  had  the  disease  find  their  way  into  the  source 
of  the  drinking  water.  In  many  cases  this  has  been  clearly 


152  PHYSIOLOGY. 

proved.     Of  course  the  dejecta  of  all  such  patients  should 
be  either  destroyed  or  thoroughly  disinfected. 

Ice  Water.  —  Although  bacteria  will  not  develop  in  a 
cold  place,  they  are  not  killed  when  water  freezes,  as  was 
formerly  supposed.  Further,  ice,  in  forming,  does  not 
throw  out  all  the  impurities,  as  was  formerly  stated.  So 
it  is  not  safe  to  drink  water  formed  from  melted  ice  unless 
the  water  of  which  that  ice  was  made  was  good  water. 
The  ice  taken  from  ponds  is  not  safe.  If  ice  is  made 
artificially  from  suitable  drinking  water,  of  course  the 
melted  product  will  be  essentially  unchanged  so  far  as  the 
composition  is  concerned.  Water  may  be  cooled  by  plac- 
ing any  ice  around  it,  and  we  may  have  the  desired  tem- 
perature without  any  admixture  of  a  dangerous  element. 

Boiling  Water.  —  When  one  cannot  get  good  drinking- 
water,  or  when  away  from  home  where  the  water  is  of 
doubtful  purity,  it  is  better  to  boil  the  water  before  using 
it,  either  as  a  drink  or  in  preparations  of  food  that  are  not 
to  be  thoroughly  cooked.  It  seems  to  be  proved  that  it 
is  better  to  heat  the  water  twice  nearly  to  the  boiling  point 
than  to  boil  hard  once  only.  The  first  heating  may  start 
the  resistant  germs  into  more  active  life,  causing  them  to 
sprout  (so  to  speak),  and  a  second  heating  several  hours 
later  may  easily  kill  them ;  whereas  it  has  been  proved 
that  one  hard  boiling  will  not  always  kill  the  germs. 

Cautions  as  to  Drinking  Water.  —  Or  if  one  uses  tea 
and  coffee,  it  is  safer  to  content  one's  self  with  these,  and 
not  drink  much  water  till  that  which  is  safe,  as  from  deep 
wells,  can  be  obtained. 

In  hot  weather,  and  especially  for  those  who  are  engaged 
in  hard  work,  it  has  been  found  that  a  little  oatmeal 
stirred  in  the  water  is  beneficial. 


FOODS.  153 

When  overheated,  avoid  drinking  much  cold  water.  Re- 
peatedly rinse  the  mouth  with  cool  water,  and  swallow  very 
little.  This  is  the  way  trainers  manage  a  horse  at  a  race, 
and  it  is  sensible  to  treat  a  man  as  carefully. 

Salts.  —  Salts  include  many  substances  besides  common 
salt.  They  aid  in  the  solution  of  various  substances  during 
digestion  and  in  other  processes.  We  cannot  live  without 
salt. 

Lime  in  the  form  of  calcium  phosphate  and  calcium  car- 
bonate is  essential,  especially  in  the  bones  and  teeth.  Iron 
is  associated  with  hemoglobin. 

Necessity  of  a  Mixed  Diet.  —  Our  experience,  together 
with  the  results  of  the  experiments  on  animals,  teaches 
that  we  could  not  live  long  if  fed  on  any  one  class  of 
foodstuffs  alone.  We  must  take  a  representative  of  each 
of  the  groups.  We  have  noticed  that  most  of  our  foods 
already  contain  more  than  one  foodstuff.  We  so  combine 
them  as  to  get  suitable  proportions.  Thus  we  eat  bread 
and  butter  (a  small  amount  of  fat  with  a  large  quantity  of 
starch  and  a  little  gluten),  meat  and  potato,  crackers  and 
cheese,  pork  and  beans,  egg  on  toast,  bread  and  milk,  rice 
and  fowl,  macaroni  and  cheese ;  they  "  go  well  together  " 
chiefly  because  they  are  complementary. 

Disadvantages  of  a  One-sided  Diet.  —  In  order  to  get 
enough  nitrogen  from  bread  alone,  one  would  have  to  eat 
about  four  pounds  a  day ;  meanwhile  twice  as  much  car- 
bon as  is  needed  would  be  taken,  thus  throwing  an  undue 
amount  of  work  upon  the  digestive  organs.  Again,  one 
would  need  to  consume  about  six  pounds  of  meat  to  get  the 
requisite  amount  of  carbon,  and  six  times  as  much  nitro- 
gen as  is  needed  would  be  taken ;  to  get  rid  of  this  extra 
nitrogen  would  severely  tax  the  kidneys  and  liver. 


154 

Effect  of  Cold  on  Appetite  for  Fats.  —  In  cold  el i mates 
a  large  amount  of  fat  is  consumed,  while  in  the  tropics 
starch  is  the  chief  food.  Our  appetites  call  for  more  of  the 
fatty  foods  during  the  winter  season. 

Proper  Diet.  —  While  common  experience  has  led  people 
to  adopt  a  mixed  diet,  the  proportions  of  the  different  food- 
stuffs is  not  always  what  it  should  be.  The  proportions 
of  the  foodstuffs  (exclusive  of  water)  may  be  roughly  stated 
as  about  I  part  of  proteid,  i  part  of  fat,  3  parts  of  carbo- 
hydrates. But  this  will  vary  somewhat  with  the  amount 
of  work  done,  and  other  varying  conditions. 

Vegetarians.  —  The  so-called  "vegetarians"  recognize 
the  need  of  proteid  food,  and  most  of  them  seek  proteid  in 
eggs,  milk,  and  cheese.  But  these  are  animal  products, 
and  the  name  " vegetarian"  is  inconsistent.  They  are 
merely  "anti-meat  eaters."  If  they  do  actually  succeed 
in  getting  enough  proteids  from  the  legumes  and  the 
grains,  the  complete  digestion  of  which  is  difficult,  they 
are,  as  Professor  Martin  says,  to  be  congratulated  on  having 
digestive  powers  that  can  stand  such  a  strain.  That  we 
are  adapted  for  using  flesh  as  part  of  our  food  is  indicated 
.in  at  least  two  anatomical  features:  ~(i)  we  have  canine 
teeth,  though  not  so  fully  developed  as  in  the  carniyora ; 
(2)  the  intestine  in  carnivora  is  very  short,  that  of  the 
herbivora  very  long,  but  in  man  intermediate.  Neverthe- 
less, it  is  undoubtedly  true  that  many  persons  eat  too  much 
meat. 

Tea.  —  Tea  owes  its  stimulating  effects  to  a  substance 
called  thein.  This  is  a  stimulant  to  the  nervous  system, 
but  if  not  too  strong  is  not  followed  by  a  subsequent 
depression.  Tea  that  is  too  strong  is  likely  to  produce 
nervousness  and  dyspepsia.  Boiling  the  tea  leaves  also 


FOODS.  155 

brings  out  the  tannic  acid  that  they  contain,  and  produces 
bad  effects. 

Coffee.  —  Coffee  owes  its  stimulating  effect  to  a  sub- 
stance called  caff  tin,  which  is  considered  identical  with 
thein.  Coffee  acts  as  a  restorative  after  hard  labor,  seem- 
ing to  retard  the  wastes  of  the  tissues  and  food.  It  is  used 
in  the  army  (also  in  penitentiaries),  not  as  a  luxury,  but  as 
a  matter  of  economy  in  the  matter  of  food  supply.  Coffee, 
used  to  excess,  frequently  causes  palpitation  of  the  heart. 

Malted  Milk.  —  Malted  and  peptonized  milk  makes  a 
valuable  drink  for  invalids  and  dyspeptics. 

Cocoa  and  Chocolate.  —  Cocoa  contains  a  stimulant 
called  theobromin.  But  unlike  tea  and  coffee,  cocoa  and 
the  preparation  from  cocoa  known  as  chocolate  are  true 
foods  by  virtue  of  the  fat  contained. 

Beef  Tea.  —  Beef  tea  and  various  beef  extracts  are  very 
beneficial.  There  is  not  enough  nourishment  in  them  to 
maintain  strength  without  other  food.  Their  nutritive 
value  has  been  somewhat  overestimated.  Their  value  is 
probably  much  more  in  their  stimulating  than  in  their 
nourishing  effect.  But  many  of  the  soups  and  drinks 
made  from  these  preparations  are  very  beneficial.  They 
refresh  the  tired  system  wonderfully.  If  the  man  who 
feels  " fagged  out"  and  takes  a  drink  of  liquor  to  " brace 
him  up,"  as  he  says,  were  to  take  a  cup  of  hot  bouillon,  he 
would  find  himself  braced  up  for  the  time,  without  any  bad 
reaction,  or  permanent  injury  to  the  system,  which  follow 
the  use  of  alcohol. 

Cooking.  —  Cooking  is  designed  to  make  food  more 
palatable  and  more  digestible.  Some  foods,  such  as  eggs, 


156  PHYSIOLOGY. 

are  as  digestible  before  they  are  cooked  as  after,  often  more 
so,  as  they  are  very  frequently  badly  cooked.  But  many 
foods  in  the  raw  state  are  unattractive,  or  even  repellent, 
whereas  cooking  usually  develops  an  agreeable  odor  and 
taste.  Cooking  should  soften  the  harder  and  tougher  tis- 
sues, such  as  cellulose  in  vegetables,  and  the  connective 
tissue  of  animal  foods.  Cooking  starch  causes  the  starch 
grains  to  swell  and  burst,  and  makes  the  starch  much  more 
digestible. 

Making  Soup.  —  If  meat  be  cut  into  small  pieces  and 
put  into  cold  water,  and  the  water  gradually  warmed,  the 
soluble  material  of  the  meat  may  be  extracted,  and  this  is 
the  principle  followed  in  making  soups. 

Boiling  Meat.  —  But  if  we  wish  to  cook  the  meat  itself, 
the  juices  should  be  retained  instead  of  withdrawn.  For 
this  purpose  boiling  water  is  poured  over  the  meat  to  co- 
agulate the  outer  layer,  and  prevent  the  extraction  of  the 
juices. 

Baking,  Roasting,  and  Broiling.  —  The  same  principle 
applies  to  baking,  roasting,  and  broiling.  The  outside  is 
subjected  to  high  heat  at  the  beginning  of  the  cooking, 
which  forms  a  layer  nearly  impervious  to  the  nutritious 
material  inside.  In  these  modes  of  cooking  it  is  very  de- 
sirable to  reduce  the  heat  applied  after  the  first  few  min- 
utes, so  that  the  interior  may  be  more  gradually  cooked ; 
this  is,  perhaps,  especially  true  in  broiling. 

Frying.  —  Frying,  as  ordinarily  done,  is  not  a  good 
mode  of  cooking ;  in  fact,  is  often  very  bad,  as  the  food  is 
frequently  penetrated  by  fat  and  rendered  very  indigestible. 
But  true  frying,  that  is,  by  immersion  in  boiling  fat,  is  a 


FOODS.  157 

good  mode  of  cooking.  This  coagulates  the  albuminous 
substance  on  the  outside,  keeps  in  the  nutritious  juices, 
and  prevents  soaking  with  the  fat.  Often  the  food  to  be 
thus  cooked  is  first  coated  with  white  of  egg,  which  is 
very  quickly  coagulated,  and  helps  form  a  protecting  out- 
side crust. 

READING.  —  Practical  Sanitary  and  Economic  Cooking, 
Abel  (Public  Health  Association);  The  Science  of  Nutri- 
tion and  the  Art  of  Cooking,  Atkinson;  Chemistry  of 
Cookery,  Williams ;  Chemistry  of  Foods  and  Nutrition, 
Atwater  (Century  Magazine,  1887-88;  also  Department 
of  Agriculture);  Eating  for  Strength,  Holbrook;  Foods, 
Smith ;  Philosophy  of  Eating,  Bellows ;  Handbook  of  In- 
valid Cooking,  Boland. 


Summary.  —  i .   Food  builds  tissue  and  maintains  energy. 

2.  The  simpler  constituents  of  foods  are  called  foodstuffs. 

3.  The  foodstuffs  are  water,  salts,  proteids,  carbohydrates,  and  fats. 

4.  Water  is  essential  to  life,  making  two  thirds  of  our  weight. 

5.  Salts  are  essential  to  life. 

6.  The  chief  proteids  are  lean  meat,  eggs,  cheese,  gluten,  etc. 

7.  The  chief  carbohydrates  are  starch  and  sugar,  derived  from  the 
grains,  vegetables,  and  fruits. 

8.  Fats  and  oils  are  obtained  from  plants  and  animals. 

9.  The  chief  source  of  impurity  in  water  is  from  bacteria,  which 
thrive  when  decaying  animal  and  vegetable  matter  are  present. 

10.  Boiling  water  may  destroy  these  germs  of  disease. 

11.  Ice  water  is  not  a  wholesome  drink. 

12.  A   mixed   diet  is  necessary,  as  no  one  food  contains  all  the 
needed  material  in  the  right  proportions  to  maintain  life  well. 

13.  Tea  and  coffee  are  slightly  stimulating,  but,  if  used  moderately, 
ordinarily  without  any  bad  reaction. 

14.  Cooking  is  to  make  food  more  palatable  and  digestible. 


158  rHYSIOLOGY. 

Questions.  —  i.    Which    class   of    foodstuffs   is    most    expensive? 
Why? 

2.  Make  a  list  of  all  the  common  foods,  naming  the  foodstuffs  in 
them. 

3.  Why  do  we  not  eat  buckwheat  cakes  and  sirup  in  summer  ? 

4.  At  what  price  are  eggs  an  expensive  food  ? 

5.  How  do  flour  and   potatoes  compare   in  economy  at  ordinary 
prices  ? 

6.  Why  are  foreigners  prejudiced  against  corn  ? 

7.  Why  is  broiling  better  than  frying  ? 

8.  Why  do  Englishmen   in   India  so  generally  suffer  from  "liver 
complaint1'  ? 


CHAPTER   X. 
THE   DIGESTIVE   SYSTEM. 

The  Object  of  Food.  — The  tissues  are  worn  out  by  their 
oxidations.  They  are  built  up  again  by  the  blood,  and 
the  blood  is  renewed  by  the  food. 

All  food  must  be  reduced  to  the  liquid  condition,  if  it 
is  not  already  liquid. 

The  Digestive  Tube.  —  The  chief  organ  in  this  work 
of  liquefying  the  food  is  the  digestive  tube,  or  "  alimentary 
canal,"  as  it  is  called.  As  the  food  passes  through  the 
digestive  tube  it  is  subjected  to  various  mechanical  and 
chemical  processes  which  liquefy  it  and  bring  it  into  such 
a  condition  that  it  can  be  absorbed  through  the  mucous 
lining  of  the  digestive  tube  and  passed  into  the  blood. 

The  Work  of  the  Digestive  Tube.  —  To  take  a  special 
instance,  a  muscle  is  in  part  worn  out  by  the  oxidation 
during  its  activity ;  to  replace  the  loss  suppose  we  take 
a  piece  of  steak.  We  cannot  substitute  this  directly  in 
the  place  of  the  worn-out  tissue.  In  digesting  the  steak 
we  must  tear  it  all  to  pieces,  and  reduce  it  to  a  liquid  form 
by  the  action  of  the  teeth  and  by  the  various  liquids  from 
the  glands  along  the  digestive  tube.  In  short,  the  muscle, 
as  such,  must  be  thoroughly  destroyed ;  in  the  liquid  pro- 
duced by  the  digestion  of  the  beef  there  is  no  trace  what- 
ever of  the  structure  of  the  beef.  But  the  blood,  taking 
this  material,  builds  muscle  which  can  hardly,  if  at  all,  be 
distinguished  from  the  original  beef. 


160  J'HYMOLOUY. 

If  the  food  taken  be  all  ready  to  build  tissue,  for  exam- 
ple, certain  forms  of  sugar,  liquid,  soluble,  and  of  the 
proper  chemical  composition,  it  will  not  need  to  go  through 
these  changes. 

In  order  to  understand  the  process  of  digestion  let  us 
first  turn  our  attention  to  the  anatomy  of  the  organs  of 
digestion. 

The  Organs  of  Digestion.  —  The  organs  of  digestion 
are  the  digestive  tube  and  the  accessory  parts,  the  masti- 
catory organs,  the  glands  in,  and  alongside  of,  the  walls 
of  the  tube. 

The  parts  of  the  digestive  tube  are  the  mouth,  the 
pharynx,  the  gullet  (or  esophagus),  the  stomach,  the  small 
intestine,  the  large  intestine. 

Brief  Description  of  the  Digestive  Organs.  —  At  the 
back  of  the  mouth  may  be  seen  the  soft  palate  with  the 
cylindrical  uvula  hanging  from  its  center.  Beyond  this 
is  the  cavity  of  the  pharynx,  which  narrows  below  into 
the  gullet,  a  red-walled,  muscular  tube,  extending  along 
the  dorsal  side  of  the  windpipe,  and  close  to  the  spinal 
column.  It  extends  the  length  of  the  thorax,  and  then 
passes  through  the  diaphragm  and  widens  into  the  stomach, 
at  the  upper  left  end  of  the  latter.  The  stomach  is  some- 
what pear-shaped,  with  the  larger  end  to  the  left.  At  the 
right  end  it  tapers  into  the  small  intestine,  the  first  foot 
or  so  of  which  is  called  the  duodenum.  Then  comes  a 
long  coil  of  the  small  intestine,  which  joins  the  shorter 
large  intestine,  ending  in  the  rectum.  Just  below  the 
diaphragm  is  the  dark-colored  liver,  overlapping  a  large 
portion  of  the  stomach.  Between  two  of  the  lobes  of  the 
liver  is  the  bile  sac  whose  duct  enters  the  duodenum  a 
short  distance  from  the  stomach.  The  pancreas  is  a  pink- 


THE  DIGESTIVE  SYSTEM. 


161 


ish  organ  of  irregular  shape  lying  along  the  stomach  and 
duodenum.  Its  duct  enters  the  duodenum  at  the  same 
point  as  the  bile  duct.  The  intestine  is  held  in  place  by 
the  mesentery,  a  thin  fold  of  transparent  membrane  folded 
closely  around  it,  and  supported  from  the  dorsal  wall  of 
the  abdominal  cavity.  Between  the  two  layers  of  the 
mesentery  are  the  branches  of  the  artery  supplying  the 
walls  of  the  intestines,  and  the  veins  that  convey  the  ab- 
sorbed food  from  the  intestine  to  the  liver. 

Digestive  Organs  of  a  Cat  or  Rabbit.  —  The  digestive  organs  will 
be  much  better  understood  if  a  cat  or  rabbit  be  dissected,  as  the  organs 
have  essentially  the  same  form  and  relations.  The  animal  may  be 
killed  by  putting  it  in  a  tight  box,  or  under  a  washbowl  with  a  small 
sponge  holding  a  tablespoonful  of  ether  or  chloroform.  It  may  then 
be  opened  by  a  slit  along  the  middle  line  of  the  ventral  surface,  from 
the  chin  to  the  pelvis.  The  diaphragm  should  be  noted  as  forming 
a  partition  between  the  cavity  of  the  chest  and  that  of  the  abdomen. 

To  Illustrate  the  Mesen- 
tery.—  To  illustrate  the  rela- 
tion of  the  mesentery  to  the 
intestine,  suspend  the  arm  in 
a  sling  made  of  a  handkerchief; 
press  the  two  thicknesses  of 
the  cloth  together  just  above 
the  arm  to  represent  the  two 
layers  of  the  mesentery. 

Model  of  Intestine  and 
Mesentery.  —  A  more  com- 
plete representation  may  be 
made  as  follows :  Material : 
piece  of  large  (one  inch  or  more 
in  diameter)  rubber  tubing, 
eight  inches  long;  sheet  of 

thin  white  court  plaster,  six  inches  by  twelve  inches ;  red,  blue,  and 
white  cord.  Lay  the  tube  across  the  middle  of  the  court  plaster;  gum 
the  plaster  snugly  around  the  tube ;  between  the  two  adjacent  layers 


Fig.  54.   Cross-section  of  Abdomen. 


1 62  rnys/oi.or,y. 

of  the  court  plaster,  where  they  meet  after  passing  around  the  tube, 
lay  the  three  kinds  of  cord,  each  frayed  out  at  one  end,  the  frayed  ends 
resting  upon  the  tube.  Moisten  the  court  plaster  and  press  the  layers 
firmly  together.  The  court  plaster  should  now  adhere  so  closely  to 
the  tube  as  hardly  to  be  seen,  and  the  two  layers  should  seem  as  one, 
in  which  appear  the  cords  representing  the  arteries,  veins,  and  lacteals. 

The  Mouth.  —  In  studying  the  mouth  and  contained 
organs,  the  student  should  not  content  himself  with  mere 
reading,  but  should  carefully  examine  his  own  mouth 
cavity  by  means  of  a  hand  glass.  We  are  apt  to  think 
of  the  mouth  as  a  cavity  of  considerable  size,  as  indeed 
it  is  when  fully  opened ;  but  we  are  not  so  likely  to  think 
how  completely  the  cavity  is  obliterated  when  the  mouth 
is  closed.  If  one  notes  the  sensations  from  the  mouth 
when  it  is  closed,  he  will  perceive  that  the  tongue  almost 
entirely  fills  the  space,  touching  the  roof  of  the  mouth,  and 
the  teeth  in  front  and  at  the  sides. 

The  Tongue.  — The  tongue  consists  chiefly  of  muscles, 
extending  in  different  directions,  thus  giving  the  tongue 
a  variety  of  motions.  The  tongue  is  the  chief  organ  of 
taste,  and  is  therefore  (with  the  sense  of  smell)  the  gate- 
keeper of  the  digestive  tube.  The  tongue  has  also  a  keen 
sense  of  touch  (the  keenest  of  any  part  of  the  body),  and 
so  is  useful  in  detecting  and  removing  any  food  particles 
that  may  remain  on  the  teeth  after  a  meal.  During 
mastication  the  tongue,  with  the  lips  and  cheek,  keep  the 
food  between  the  teeth.  When  the  morsel  of  food  is 
sufficiently  masticated,  the  tongue  pushes  it  back  into  the 
pharynx  to  be  swallowed. 

The  Teeth.  — The  teacher  can  usually  obtain  a  lot  of 
teeth  from  the  dentist  for  the  asking.  These  should  be 
cleaned  before  using  them  in  the  class.  Use  pearline 


THE  DIGESTJl'E  SYSTEM. 


I63 


or  any  washing  soda.  If  there  be  enough  time,  let  each 
pupil  make  a  drawing  of  one  of  each  of  the  four  kinds  of 
teeth ;  and  it  would  be  well  to  draw  both  a  front  (outer 
surface)  and  a  side  view  (surface  adjacent  to  another 
tooth)  of  each  of  the  four  kinds. 


Longitudinal  Section 


Side  View 


Face  View 


Crown 


Neck 


Root 


Hole  for  Blood  Tubes  and  Nerves     - 
Fig.  55.    Parts  of  a  Tooth.     (Incisor.) 

External  Features  of  a  Tooth.  —  Examine  one  of  the 
front  teeth.  It  has  the  following  parts  : — 

1.  The  crown,  the  part  that  is  above  the  gum. 

2.  The  root,  the  part  that  was  buried  beneath  the  gum. 

3.  The  neck,  a  more  or  less  constricted  part,  dividing 
the  crown  from  the  root ;  it  is  normally  at  about  the  sur- 
face of  the  gum. 

4.  A  hole  at  the  tip  of  the  root. 

To  make  a  Section  of  a  Tooth.  —  Let  each  pupil  prepare  a  longi- 
tudinal section  of  a  tooth  as  follows :  Imbed  a  tooth  in  a  little  sealing 
wax  on  the  end  of  a  spool,  cork,  or  block  of  wood.  With  a  grindstone 
grind  away  one  half,  showing  the  pulp  cavity  to  the  tip  of  the  root  as 
in  Fig.  55.  Make  a  drawing  of  the  surface  thus  exposed,  naming  the 
parts.  If  human  teeth  cannot  be  obtained,  almost  any  kind  will  serve. 
Let  each  pupil  keep  his  preparation. 


164  rnvsioi.OC,Y. 

Structure  of  a  Tooth.  —  i.  The  pulp  cavity,  communi- 
cating with  a  hole  in  the  tip  of  the  root,  through  which 
the  nerve  and  blood  tube  entered. 

2.  The  bulk  of  the  tooth  is  made  up  of  a  substance 
called  dentine  (ivory). 

3.  The  crown  of  the  tooth  has  a  covering  of  enamel,  a 
very  hard  substance. 

4.  The  root  is  covered  with   a  bony  substance  called 
cement. 

The  Kinds  of  Teeth  and  their  Arrangement  —  Begin- 
ning at  the  middle  of  the  front  of  the  mouth,  there  are  (in 
the  normal  adult)  eight  teeth  in  each  half  jaw :  two  in- 
cisors, one  canine,  two  bicuspids  (or  premolars),  and  three 
molars. 

Dental  Formula.  — The  kinds  and  arrangement  of  teeth 
are  often  expressed  by  a  dental  formula,  in  which  the  nu- 
merators indicate  the  upper  jaw  and  the  denominators  the 
lower,  thus :  If,  C^,  PMf ,  Mf  (for  one  side  of  the  head). 

Incisors.  —  The  crown  of  an  incisor  is  chisel  shaped ; 
but  the  root  is  flattened  in  the  opposite  direction,  i.e.  at 
right  angles  to  the  jaw,  instead  of  parallel  to  it,  as  is  the 
case  with  the  crown.  Look  at  a  skull  from  which  the 
teeth  have  been  extracted  in  order  to  see  the  cavities  into 
which  the  teeth  fitted. 

Canines.  — The  canine  tooth  has  a  conical  crown,  and  a 
longer  root  than  the  incisor. 

Bicuspids.  —  The  bicuspid  has  two  points. 

Molars.  —  The  molar  has  a  cuboidal  crown,  and  usually 
two  or  three  roots. 

The  Milk  Teeth. —  The  thirty-two  teeth  of  the  perma- 
nent set  were  preceded  by  a  temporary  set  of  twenty  milk 


THE  DIGESTIVE  SYSTEM 


I65 


teeth.  Because  the  first  set  is  temporary  it  should  not 
therefore  be  neglected.  Cavities  in  these  should  be  filled 
and  the  teeth  kept  clean.  Before  the  temporary  set  has 
gone  the  first  of  the  permanent  set  appear.  The  first  of 


KINDS   OF   TEETH 
Incisors     :::••— 


Upper 


TIME   OF   APPEARANCE 

7tb  Month 

9th       " 

18th      " 


TEMPORARY   SET 
Upper 


Lower 
PERMANENT   SET 


Fig.  56.    TEETH:  Kinds,  Arrangements,  and  Times  of  Appearance. 

these,  often  called  the  "  six-year  molars,"  are  just  back  of 
the  hindermost  "milk  molars."  These  should  receive 
especial  care,  as  they  will  never  be  replaced.  Any  begin- 
ning of  decay  in  them  ought  to  receive  prompt  attention. 


1 66 

The  Care  of  the  Teeth.  — The  teeth  need  careful  atten- 
tion. They  should  be  thoroughly  brushed  at  least  twice  a 
day,  on  rising  and  on  going  to  bed.  It  would  be  better  to 
clean  them  after  each  meal  also.  If  a  tooth  powder,  recom- 
mended by  a  reliable  dentist,  is  not  used,  a  good  white 
castile  soap  will  serve  well.  It  is  better  to  use  tepid  water. 
If  the  teeth  are  not  thoroughly  cleansed  the  particles  of 
food  which  remain  will  soon  begin  to  decay.  This  decay 
is  caused  by  the  growth  of  germs,  usually  some  kind  of 
bacteria,  and  the  decay  thus  begun  is  likely  to  develop 
acids  which  attack  the  limy  material  of  which  the  teeth  are 
composed.  When  it  is  necessary  to  take  acid  medicines, 
care  should  be  taken  not  to  let  them  come  in  contact  with 
the  teeth.  Sweet  substances  are  very  likely  to  decompose 
and  form  acids ;  so  we  must  clean  the  teeth  after  eating 
candies.  Toothpicks  are  useful  in  removing  the  larger 
particles.  But  in  using  toothpicks  care  should  be  taken 
not  to  dislodge  fillings.  The  teeth  should  be  examined 
twice  a  year  by  a  dentist,  and  any  cavities  promptly  filled. 

The  Salivary  Glands.  —  The  salivary  glands  make  the 
saliva  and  pour  it  into  the  mouth.  There  are  three  pair  of 
salivary  glands  —  the  parotid,  just  back  of  the  angle  of  the 
jaw,  under  the  ear ;  its  duct  runs  forward  under  the  skin 
of  the  cheek,  and  opens  on  the  inside  of  the  cheek  opposite 
the  second  molar  of  the  upper  jaw.  The  submaxillary 
gland  lies  under  the  angle  of  the  jaw  ;  its  duct  opens  under 
the  tongue  near  the  front  of  the  mouth.  The  sublingual 
gland  is  in  front  of  the  submaxillary  and  empties  near  the 
same  place  as  the  .submaxillary. 

Dissection  of  the  Salivary  Glands.  —  The  salivary  glands  of  a 
rabbit  or  cat  may  be  found  near  the  base  of  the  ear  and  under  the  angle 
of  the  jaw  by  removing  the  skin  from  the  side  of  the  head  and  neck. 


THE  DIGESTIVE  SYSTEM.  1 67 

Salivary  Ducts  in  Our  Mouths.  —  If  the  inside  of  one's  cheek  be 
examined  by  the  use  of  a  hand  mirror,  the  opening  of  the  duct  from  the 
parotid  gland  may  be  seen  opposite  the  second  molar  of  the  upper  jaw. 
It  usually  looks  like  a  pink  and  white  spot,  resembling  a  wound  of  a 
bee  sting.  Sometimes  saliva  may  be  seen  issuing  from  it. 

Action  of  the  Salivary  Glands.  —  The  salivary  glands 
pour  into  the  mouth  a  liquid  which  they  manufacture  from 
materials  taken  from  the  blood.  In  structure  the  gland 
may  be  compared  to  a  bunch  of  grapes^  the  grapes  repre- 
senting the  little  cavities,  with  a  wall  of  cells  that  make 


Mucous  Membrane 


Duct  of  Gland 


Secreting  Cells 


Fig.  57.     Diagram  of  a  Salivary  Gland.     (.After  Landois  and  Stirling.) 

the  saliva.  From  these  cavities  the  liquid  passes  into  the 
individual  duct,  represented  by  the  stem  of  a  single  grape ; 
many  of  these  unite  to  form  the  main  stem,  which  corre- 
sponds to  the  main  duct.  A  rich  network  of  capillaries 
surrounds  the  gland ;  when  the  gland  is  at  work  it  receives 
more  blood ;  the  liquid  part  of  the  blood  (plasma)  soaks 
out  through  the  capillary  walls  and  surrounds  the  gland ; 
it  is  now  called  lymph  ;  from  the  lymph  the  gland  directly 
obtains  its  material. 


168  PHYSIOLOGY. 

Nerve  Control  of  Salivary  Glands.  -The  glands  are 
doubly  dependent  on  nerve  control :  — 

1.  Through  the  control  of  the  arterial  muscles  by  the 
nerves  the  amount  of  blood  sent  to  the  glands  is  regulated. 

2.  Nerves  also  go  to  the  cells  of  the  gland  to  control 
their  activity.     When  we  taste,  smell,  see,  or  even  when 
we  think  of,  some  delicious  food  the  mouth  may  "water," 
as  we  say,  i.e.  the  salivary  glands  are,  by  reflex  action, 
stimulated  to  activity ;  on  the  other  hand,  some  emotions, 
such  as  fear,  check  the  flow  of  saliva. 

Saliva  and  its  Uses.  —  The  saliva  is  mostly  water,  and, 
when  we  are  not  eating,  serves  to  keep  the  mouth  moist. 
The  water  of  the  saliva  soaks  the  food  during  mastication 
and  helps  the  process  of  grinding ;  it  enables  us  to  taste 
by  dissolving  any  food  that  is  soluble ;  it  further  enables 
us  to  swallow  what  would  otherwise  be  a  dry  powder. 
The  special  element  of  the  saliva,  ptyalin,  has  the  power 
of  changing  starch  to  sugar. 

Amount  of  Saliva.  —  The  amount  of  saliva  secreted 
daily  is  estimated  at  three  pints.  Of  course  the  glands 
should  be  allowed  to  rest  between  meals.  The  habit  of 
chewing  gum,  though  supposed  to  aid  digestion,  undoubt- 
edly does  far  more  harm  than  good.  During  the  resting 
period  the  glands  accumulate  material  for  the  active  work 
of  secretion,  for  there  is  no  sac  in  which  to  store  the 
saliva,  and  it  must  be  made  as  fast  as  it  is  needed. 

Character  of  Salivary  Ferment.  —  "  The  character  of 
action  of  salivary  ferment  is  further  defined  by  experi- 
ments showing  :  i,  that  it  is  destroyed  by  boiling;  2,  that 
its  action  is  delayed  or  suspended  at  a  low  temperature, 
most  pronounced  at  about  body  temperature  (37°  C); 
3,  that  it  acts  best  in  a  neutral  or  in  a  faintly  alkaline 


THE  DIGESTIVE  SYSTEM.  169 

medium,  not  at  all  in  an  acid  medium,  or  in  too  strong  an 
alkaline  medium ;  4,  that  it  has  almost  indefinite  power, 
if  the  product  of  its  own  action  (sugar)  is  not  suffered  to 
accumulate.  In  all  these  respects,  with  the  exception 
of  the  third,  the  salivary  ferment  resembles  ferments  in 
general,  which  are  destroyed  by  heat,  delayed  by  cold, 
and  are  limited  in  their  action  only  by  the  accumulated 
product  of  such  action."  —  WALLER. 

Enzymes.  —  Ptyalin  is  a  type  of  a  group  of  bodies 
called  unorganized  ferments,  or  enzymes.  These  ferments 
are  the  agents  that  produce  the  peculiar  chemical  changes 
that  are  the  chief  part  of  digestion. 

Mucous  Glands  and  Mucus.  —  Besides  the  salivary 
glands,  there  are  great  numbers  of  simple  glands  in  the 
mucous  membrane  lining  the  mouth.  These  secrete  a 
glairy  substance  called  mucus. 

Experiments  with  Digestive  Liquids.  —  It  may  be  proved  by 
experiment  that  saliva  turns  starch  to  grape  sugar  in  an  alkaline  solu- 
tion and  at  the  proper  temperature.  Also  that  pepsin  dissolves  proteids 
in  an  acid  (hydrochloric)  at  the  right  temperature.  The  proteid  is 
turned  to  peptone,  and  becomes  soluble  and  diffusible,  capable  of 
absorption  through  the  walls  of  the  stomach  and  intestine.  We  find 
that  the  different  elements  of  the  pancreatic  juice  can,  in  alkaline  solu- 
tion, and  at  the  right  temperature,  emulsify  fats,  turn  proteid  to  pep- 
tone, and  convert  starch  into  grape  sugar. 

The  Pharynx.  — The  cavity  back  of  the  mouth,  beyond 
the  soft  palate,  is  the  pharynx.  The  pharynx  is  a  funnel- 
shaped  cavity,  communicating  above  with  the  passages 
from  the  nostrils ;  in  front  it  opens  into  the  mouth  ;  below 
it  connects  with  the  windpipe,  through  the  glottis,  and 
with  the  gullet,  which,  as  we  have  seen,  lies  just  back  of 
the  windpipe. 


PHYSIOLOC.Y. 


Position  of  Organs  during  Respiration.  —  In  quiet 
respiration  the  tongue  nearly  fills  the  mouth.  The  base 
of  the  tongue  is  nearly  covered  by  the  soft  palate,  which 
curves  downward  from  the  hard  palate,  and  by  the  epi- 
glottis projecting  upward  from  below.  The  glottis  is 
open  and  the  gullet  is  closed.  Air  enters  the  nostrils, 
passes  along  the  nasal  passages  above  the  hard  palate, 
back  of  the  soft  palate  and  epiglottis,  through  the  open 
glottis  into  the  windpipe,  and  on  to  the  lungs. 


Hard  Palate ------ 


Eustachian  i  ube 


•--  Soft  Palate,  Down 


Pharynx 

-  Epiglottis,  Raised 

-—Gullet,  Closed 
Glottis,  Open 


Fig.  58.     Diagram,  showing  the  Positions  of  the  Organs  of  the  Mouth  and 
Throat  during  Breathing. 

The  Process  of  Swallowing.  —  When  the  morsel  of 
food  is  ready  to  be  swallowed  the  tongue  pushes  it  back 
into  the  pharynx ;  the  soft  palate  is  raised  to  shut  off  the 
passage  into  the  nasal  cavity ;  the  larynx  is  pulled  upward 
and  forward ;  the  epiglottis  is  pulled  down  over  the  glottis, 
or  opening  of  the  windpipe ;  and  the  base  of  the  tongue 
extends  back  over  the  epiglottis ;  thus  the  air  passages, 
above  *md  below,  are  shut  off,  and  the  food  passes  over 
the  epiglottis  into  the  gullet.  The  muscles  of  the  pharynx 


THE  DIGESTIVE  SYSTEM. 


171 


also  do  their  part  in  pushing  the  food  along.  As  soon  as 
the  food  has  passed  over  the  epiglottis,  the  epiglottis  rises 
to  its  upright  position,  and  the  soft  palate  drops  back  to 
its  place,  leaving  the  air  passages  again  open. 

Breathing  and  Swallowing.  —  It  is  to  be  observed  that 
the  food  tube  and  the  air  tube  cross,  and  that  the  pharynx 
is  their  crossing.  As  we  are  swallowing  only  a  small 
part  of  the  time,  the  passageway  naturally  stands  open  to 
the  air ;  and  when  we  swallow,  the  parts  are,  by  muscular 


Eustachian  Tube 

-  Soft  Palate,  Raised 

-  Food 

....  Epiglottis.  Down 

-  Gullet,  Open 

•-  Glottis,  Closed 


Fig.  59.     Diagram,  showing  the  Positions  of  the  Organs  of  the  Mouth  and 
Throat  during  Swallowing. 

effort,  temporarily  adjusted  for  this  work.  There  is  a 
spring  switch  (to  borrow  a  term  from  the  railway)  which 
keeps  the  track  open  for  the  air,  which  is  all  the  time 
passing ;  but  when  the  food  comes  along,  the  switch  must 
be  held  open  for  it  until  it  has  passed. 

Structure  and  Action  of  the  Gullet.  —  The  gullet  has 
an  outer  muscular  coat  and  an  inner  mucous  coat.     The 


172  PHYSIOLOGY. 

muscular  coat  has  two  layers,  an  inner  with  circularly 
arranged  fibers,  and  an  outer  layer  with  longitudinally 
arranged  fibers.  When  the  food  enters  the  gullet  the 
muscle  fibers,  especially  the  circular  fibers,  shorten,  and 
by  a  wave-like  action  push  the  mass  rapidly  along  into  the 
stomach.  The  first  part  of  swallowing  is  voluntary ;  but 
after  the  bolus  has  entered  the  gullet  the  action  is  involun- 
tary. The  mucous  lining  of  the  gullet  has  many  mucous 
glands  which  lubricate  the  passageway  by  the  mucus  which 
they  secrete. 

Illustration  of  Passage  through  the  Gullet.  —  The  passage  of  the 
food  through  the  gullet  may  be  illustrated  as  follows  :  Let  several  per- 
sons hold  a  large  rubber  tube  with  their  hands  in  contact.  Put  an  egg- 
shaped  piece  of  wet  soap  in  the  tube.  The  first  hand  is  shut  and 
pushes  the  soap  along  into  the  part  of  the  tube  held  by  the  next  hand ; 
this  hand  now  compresses  the  tube,  while  the  first  hand  remains  clinched  ; 
and  so,  in  turn,  the  object  is  pushed  the  whole  length  of  the  tube. 

The  Stomach.  —  Just  beyond  the  diaphragm  the  diges- 
tive tube  widens  suddenly,  forming  the  stomach ;  the 
stomach  is  an  oval  sac  lying  just  beneath  the  diaphragm, 
with  the  large  end  to  the  left  and  the  small  end  to  the 
right.  The  smaller  end,  by  narrowing,  becomes  the  small 
intestine.  When  the  stomach  is  empty  it  collapses,  as  its 
walls  are  soft  and  flexible.  When  distended  it  may  hold 
three  pints,  or  when  abnormally  distended  even  more. 

The  Coats  of  the  Stomach.  —  The  stomach  and  intestines  have  four 
coats,  in  the  following  order,  beginning  at  the  outside  :  the  peritoneum, 
the  muscular,  the  submucous,  and  the  mucous  coats.  The  muscular 
coat  of  the  stomach  consists  of  three  layers,  distinguished  by  the 
arrangement  of  the  fibers,  a  circular  layer,  a  longitudinal  layer,  and  an 
oblique  layer.  The  mucous  lining  is  somewhat  loosely  attached  to 
the  muscular  coat  by  the  intervening  submucous  coat,  and  when  the 
stomach  collapses  the  mucous  coat  is  thrown  into  folds,  usually  running 
lengthwise. 


THE   DIGESTIVE  SYSTEM. 


173 


The  Gastric  Glands.  —  In  the  inner  surface  of  the 
mucous  membrane  are  many  holes.  These  are  the  mouths 
of  the  ducts  of  the  gastric  glands.  If  a  duct  is  traced 
inward,  it  is  found  to  divide  into  several  branches,  usually 
two  or  three.  These  gastric  glands  vary  somewhat  in  their 
structure  in  different  parts  of  the  stomach. 

The  Gastric  Juice.  —  The  liquid  secreted  by  the  differ- 
ent glands  also  varies  considerably,  but  the  liquid  as  a 
whole  is  called  the  gastric  juice.  The  gastric  juice  is 


GULLET 


Fig.  60.    Longitudinal  Section  of  Stomach,  showing  Gastric  Glands  in  Position. 
(Dorsal  View.     Mucous  Coat  Unduly  Thickened.) 

chiefly  water,  containing  a  ferment,  or  enzyme,  called 
pepsin,  and  a  small  amount  of  acid.  The  amount  of 
gastric  juice  secreted  daily  has  been  estimated  at  from 
five  to  ten  quarts.  Of  course,  we  must  bear  in  mind  that 
nearly  all  of  this  is  again  absorbed  from  the  digestive  tube, 
and  is  not  a  permanent  loss  to  the  body. 

Blood  Supply  of  the  Stomach.  —  The  mucous  mem- 
brane is  abundantly  supplied  with  blood  tubes,  but 
during  the  time  of  its  rest  the  blood  flow  here  is 


174 


PHYSfOLOGY. 


Mouth  of  Gland 


Epithelium 


Cells 


diminished,  and  the  membrane  is  comparatively  pale. 
But  as  soon  as  food  is  introduced  into  the  stomach  the 
blood  flow  is  greatly  increased,  and  the  mucous  membrane 
becomes  red.  This  blood  supply  gives  the  glands  the  ma- 
terials with  which  they  manufacture  the  gastric  juice.  At 

the  same  time  the  cells  of 
the  glands  are  stimulated 
to  action,  and  the  secre- 
tion is  poured  out  rapidly. 
The  alkaline  saliva  also 
aids  in  stimulating  the 
i  secretion  of  the  gastric 
juice. 

The  Work  of  the 
Gastric  Juice. — The  spe- 
cial work  of  the  gastric 
juice  is  accomplished  by 
the  pepsin,  aided  by  the 
acid ;  these  convert  pro- 

teids  into  a  soluble  substance,  called  peptone,  which  can 
be  absorbed  through  the  walls  of  the  digestive  tube  into 
the  blood. 

Rennet  and  Rennin.  —  Rennet,  used  in  cheese  making,  is  a  familiar 
substance  obtained  from  the  fourth  stomach  of  the  calf.  When  milk 
enters  the  stomach  it  is  curdled  ;  that  is,  the  casein  previously  dissolved 
in  the  liquid  milk  is  coagulated.  This  curdling,  or  coagulation,  is  at- 
tributed to  a  ferment  in  the  gastric  juice  called  rennin,  and  it  seems  to 
be  entirely  distinct  from  pepsin. 

Churning  Action  of  the  Stomach.  —  At  the  same  time 
all  the  food  is  soaked  by  the  gastric  juice,  the  process  being 
greatly  assisted  by  the  churning  motion  of  the  stomach 
caused  by  the  action  of  the  muscular  coat.  The  food  is 
thus  gradually  re'duced  to  a  pulpy  mass  called  chyme. 


Connective  Tissue 


Fig.  6 1 .   Three  Glands  of  the  Stomach  — 
Cardiac  Part. 


THE  DIGESTIVE  SYSTEM.  1/5 

During  the  first  part  of  digestion  in  the  stomach  the  thick 
ring  of  circular  fibers  called  the  pylorus  (gatekeeper)  around 
the  opening  of  the  stomach  into  the  intestine  keeps  the 
passage  nearly  closed,  leaving  a  small  orifice  for  liquids 
only.  But  as  the  food  is  reduced  to  the  proper  condition 
the  pyloric  muscles  relax  and  allow  the  chyme  to  pass  into 
the  intestine.  And  at  last  any  indigestible  substances  are 
usually  allowed  to  pass. 

Sphincter  Muscles.  —  Such  rings  of  muscular  fibers, 
guarding  openings,  are  called  sphincter  muscles.  There 
is  a  similar  one  at  the  anal  opening. 

Time  of  Stomach  Digestion.  —  The  time  required  for 
the  digestion  of  any  ordinary  meal  is  from  three  to  four 
hours,  though  this  may  be  much  longer  if  very  indigestible 
substances  have  been  eaten,  or  if  the  condition  of  the  body 
or  mind  is  such  as  to  retard  the  process  of  digestion. 

Absorption  from  the  Stomach.  —  Some  parts  of  the 
food  that  are  already  digested,  or  such  matters  as  are  sol- 
uble, e.g.  water  containing  sugar,  peptone,  salts,  etc.,  may 
be  absorbed  immediately  through  the  walls  of  the  mouth 
and  stomach  into  the  blood  capillaries.  Recent  experiments 
show  that  the  amount  of  absorption  from  the  stomach  is 
much  less  than  was  formerly  supposed  ;  water,  for  instance, 
"  when  taken  alone,  is  practically  not  absorbed  at  all  in  the 
stomach.  As  soon  as  water  is  introduced  into  the  stomach 
it  begins  to  pass  out  into  the  intestine,  being  forced  out  in 
a  series  of  spurts  by  the  contractions  of  the  stomach." 

Chyme.  —  The  rest  of  the  food,  now  called  chyme,  is 
passed  on  into  the  small  intestine.  It  is  acid,  and  in  a 
liquid  or  semiliquid  condition.  Chyme,  as  it  enters  the 
intestine,  is  a  mixture  of  digested,  partly  digested,  and  un- 


1 76 


PHYSIOLOGY. 


digested  materials.  Some  of  the  starch  has  been  changed 
to  sugar,  but  only  a  small  part,  owing  to  the  short  time  of 
mastication.  The  bulk  of  the  starch  is  unchanged.  Some 
of  the  proteid  is  already  changed  to  peptone.  Part  is  still 
proteid,  while  part  is  in  an  intermediate  stage  between 
proteid  and  peptone.  Fat  is  essentially  unchanged,  but  is 
melted  by  the  heat  of  the  mouth  and  stomach,  and  is  more 
or  less  divided  into  small  drops  by  mastication  and  the 
movements  of  the  stomach.  For  instance,  in  eating  bread 
and  butter,  the  melting  butter  will  be  finely  mixed  with  the 
bread  as  it  is  chewed.  The  water  in  the  chyme  was  partly 
taken  as  such,  and  partly  derived  from  the  saliva  and 
gastric  juice.  There  are  also  present  ptyalin,  pepsin, 

mucus,  salts,  and  some  indigesti- 
ble substances.  At  intervals  the 
sphincter  muscles  of  the  pylorus 
relax,  and  the  contractions  of  the 
stomach  send  the  liquid  mixture 
into  the  intestines  by  spurts. 

The  Intestine.  —  The  small  in- 
testine has  essentially  the  same 
structure  as  the  parts  of  the  diges- 
tive tube  already  studied,  namely, 
a  mucous  lining  beset  with  an  im- 
mense number  of  tubular  glands, 
called  intestinal  glands.  These 

secrete  a  liquid  collectively  called  the  intestinal  juice,  whose 
exact  work  is  not  well  known,  but  which  may  be  said  to 
complete  the  work  of  the  other  secretions.  The  intestine 
has  also  a  muscular  coat  with  circular  and  longitudinal 
fibers.  And  the  muscular  coat  does  the  same  work  of 
mixing  the  juices  with  the  food  and  of  moving  it  along. 


Fig.  62.  Horizontal  Section 
through  the  Mucous  Membrane  of 
the  Intestine,  showing  Intestinal 
Glands  in  Transverse  Section. 
(Highly  Magnified.) 


THE  DIGESTIVE  SYSTEM. 


177 


Bile  and  Pancreatic  Juice.  —  Soon  after  the  chyme 
enters  the  small  intestine  it  has  poured  upon  it  two  liquids, 
which  enter  the  intestine  in  one  common  stream  ;  these 
are  the  bile  and  the  pancreatic  juice.  These  juices  come 
from  two  large  compound  glands,  the  liver  and  pancreas, 


Fig.  63.     Diagram  of  Portal  Circulation. 

that  lie  close  to  the  stomach.  Their  ducts  join  before  they 
enter  the  intestine  into  which  these  juices  are  emptied  a 
few  inches  beyond  the  stomach. 

The  Portal  Circulation.  —  The  liver  receives  blood 
from  two  sources,  —  a  branch  of  the  aorta  and  the  portal 
vein.  The  portal  vein  is  formed  by  the  union  of  veins 
from  the  stomach,  intestine,  pancreas,  and  spleen.  Unlike 


1/8  PHYSIOLOGY. 

other  veins,  the  portal  vein  divides  and  subdivides,  forming 
capillaries  which  ramify  through  the  liver.  The  blood  is 
again  collected  by  veins,  forming  the  hepatic  vein  which 
empties  into  the  postcaval  vein  close  to  the  diaphragm. 
From  the  blood  the  liver  manufactures  at  least  two  impor- 
tant substances,  —  the  bile  and  liver  starch,  or  glycogen. 

Functions  of  Bile.  —  The  bile  is  secreted  all  the  time, 
but  more  actively  during  digestion.  The  part  made  while 
digestion  is  not  going  on  is  stored  in  the  bile  sac.  The 
functions  of  the  bile  are  still  poorly  understood.  But  the 
following  are  believed  to  be  a  part  of  its  work :  — 

1.  It  is  believed  to  aid  in  emulsifying  the  fats. 

2.  It  is  supposed  to  aid  in  the  absorption  of  fat. 

3.  The  bile,  to  a  certain  extent,  is  waste  matter ;  so  the 
liver  is  an  organ  of  excretion  as  well  as  an  organ  of  secretion. 

4.  It  is  found  that  if,  for  any  cause,  the  bile  is  prevented 
from  entering  the  intestine,  constipation  follows,  and  the 
contents  of  the  large  intestine  have  a  much  more  fetid 
odor  than  usual.     The  bile  itself  readily  putrefies ;  hence 
it  is  concluded   that  the  bile  has  no  positive  antiseptic 
properties,  but  in  some  indirect  way  retards  putrefaction. 

The  liver,  from  its  size,  ought  certainly  to  be  of  great 
importance  in  the  body ;  it  is  the  largest  gland  in  the 
body,  and  receives  one  fourth  of  the  blood. 

The  Work  of  the  Pancreatic  Juice.  —  The  pancreatic 
juice  acts  on  all  the  principal  classes  of  foodstuffs :  — 

1.  A  ferment  in  it  called  amylopsin  acts  on  starches, 
changing  them  to  sugar,  even  more  energetically  than  the 
ptyalin  of  the  saliva. 

2.  Another  constituent  of   pancreatic  juice  is  trypsin  ; 
like  the  pepsin  of  gastric  juice,  this  ferment  has  the  power 
of  changing  proteids  to  peptones. 


THE  DIGESTIVE  SYSTEM.  179 

3.  The  pancreatic  juice  also  acts  on  the  fats  in  two 
ways :  — 

(a)  It  emulsifies  them,  i.e.  the  fat  is  divided  into  exceed- 
ingly fine  drops,  each  enveloped  in  a  coating  of  albuminous 
substance.    An  emulsion  can  be  made  artificially  by  shak- 
ing together  water,  oil,  and  white  of  egg.     The  shaking 
breaks  the  oil  into  fine  drops,  which  would  soon  gather 
again  if  no  other  substance  were  present ;  but  it  is  sup- 
posed that  the  albumen  forms  a  thin  coating  around  each 
droplet,  enabling  it  to  remain  distinct  in  the  liquid. 

(b)  The  fats  are  also  acted  on  chemically  by  steapsin, 
another  ferment  of  the  pancreatic  juice ;  they  are  decom- 
posed with  the  formation   of   free  fatty  acids,  and  thus 
more  fully  prepared  to  be  absorbed  and  to  build  up  the 
tissues.     These  free  fatty  acids  aid  in  the  work  of  emulsi- 
fying the  rest  of  the  fat. 

Review  of  Digestive  Liquids.  —  Saliva  acts  only  on 
starch,  gastric  juice  on  proteids,  bile  on  fats,  whereas 
pancreatic  juice  acts  on  all  three,  and,  probably,  more 
energetically  than  the  above-named  liquids. 

Intestinal  Juice. — The  intestinal  juice  contains  a  fer- 
ment, called  invertin,  which  changes  cane  sugar  to  dextrose 
which  is  a  variety 
of  grape  sugar.  vim 

Acids  and  Al- 
kalies in  Diges- 
tion.  —  The  bile 

and  the  pancreatic         intestinal  cianc-s 

juice  are  alkaline, 

Fig.  64.     Mucous  Membrane  of  Small  Intestine 

and  overcome  the 

acidity  of  the  chyme,  as  the  acidity  of  the  gastric  juice 

in  the  stomach  overcame  the  alkalinity  of  the  saliva. 


180  PHYSIOLOGY. 

Summary.  —  I .  The  chief  work  in  digestion  is  to  render  the  food 
liquid,  soluble,  and  in  condition  to  be  absorbed  and  become  part  of  the 
blood. 

2.  The  digestive  system  consists  of  a  long  tube,  through  which 
the  food  passes,  being  subjected  to  mechanical  and  chemical  processes 
to  liquefy  and  otherwise  make  the  food  ready  to  become  blood. 

3.  The  teeth  grind  the  food. 

4.  The  food  is  soaked  and  acted  on  by  the  saliva,  gastric  juice, 
intestinal  juice,  bile,  and  pancreatic  juice. 

5.  These  liquids  are  formed  from  the  blood  by  glands.     A  gland 
is  a  structure,  usually  tubular  or  saclike,  surrounded   by  capillaries, 
which  give  off  lymph  around  the  gland.     The  gland  cells  take  part 
of  the  lymph  and  form  the  "secretion,"  which  is  usually  poured  out 
on  a  surface  by  means  of  a  narrow  tube,  or  duct. 

6.  The  salivary  glands,  pancreas,  and  liver  are  compound  glands. 
The  gastric  and  intestinal  glands  are  simple. 

7.  The  first  part  of  swallowing  is  voluntary.     Through  the  gullet 
the  food  is  pushed  by  the  shortening  of  the  circular  muscle  fibers. 

8.  The   liver  receives   blood   from    the    hepatic   artery   and   from 
the  portal  vein,  but  is  drained  by  one  vein,  the  hepatic,  which  empties 
into  the  postcaval  vein. 

9.  Saliva  acts   only  on  starch,  gastric  juice  on  proteids,  bile   on 
fats  ;  pancreatic  juice  acts  on  all  three  of  these  foodstuffs. 

Questions.  —  i.  Why  does  the  physician  examine  the  tongue  of  his 
patient? 

2.  What  is  the  "mumps"? 

3.  Why  is  one  more  likely  to  choke  if  he  thinks  about  the  process 
of  swallowing? 

4.  What  are  the  peculiarities  of  a  cow's  stomach? 

5 .  What  is  the  meaning  of  biliousness  ? 

6.  Why  is  there  a  difference  in  the  length  of  the  intestine  in  a  cat 
and  a  sheep? 

7.  What  is  colic? 


CHAPTER   XI. 


Lymph 
Duct 


ABSORPTION  — DIGESTION   COMPLETED. 

Absorption.  —  The  mucous  membrane  of  the  small 
intestine  is  thrown  into  ridges,  but,  unlike  those  of  the 
stomach,  they 
run  transversely. 
Again,  while  the 
folds  in  the  lining 
of  the  stomach 
are  temporary, 
these  are  perma- 
nent. They  serve 
to  increase  the 
surface  of  the  lin- 
ing, and  to  retard 

the  passage  Of  the         Mesenterlc 
.     -  .     Lymph  Veins 

food  material,  and       (Fats) 
so  to  aid  the  pro- 
cess of  digestion 
and  of  absorption. 

Villi.  — Fur- 
ther, the  surface 
of  the  mucous 
membrane  of  the 
small  intestine  is  thickly  beset  with  little  cylindrical  pro- 
jections, like  the  "  pile  "  on  velvet.  These  projections  are 

181 


Lymph 
Glands  ""•". 


Lacteal  s 


Fig.  65.     Plan  of  Absorption. 


1 82  PHYSIOLOGY. 

called  villi  (singular,  villus).  The  villi  greatly  increase 
the  absorbing  surface  of  the  small  intestine.  In  each 
villus  is  a  network  of  blood  capillaries,  and  the  beginning 
of  lymphatic  capillaries  called  lacteals. 

Routes  of  Different  Foods  after  Absorption.  —  In  the 

villi  the  largest  part  of  the  work  of  absorption  is  done. 
The  fats  are  absorbed  by  the  lymph  capillaries,  or  lacteals, 
and  the  rest  of  the  foods  by  the  blood  capillaries.  It 
should  be  carefully  noted  that  nearly  all  of  the  foods  but 
the  fats  go  at  once  to  the  liver,  through  the  portal  vein ; 
but  the  fats  are  carried  by  the  main  lymph  duct  (the 
thoracic  duct)  to  be  emptied  into  the  subclavian  vein  in 
the  neck ;  hence  do  not  directly  pass  through  the  liver. 

Diffusion,  Osmosis,  and  Dialysis.  —  If  a  solution  of  salt  and  one 
of  sugar  are  brought  into  contact,  they  will  gradually  mix  by  diffusion. 
If  these  two  solutions  are  separated  by  parchment,  they  will  still  diffuse 
through  the  membrane  and  mingle.  This  is  osmosis.  Since  substances 
differ  in  the  readiness  with  which  they  pass  through  a  membrane,  they 
may  be  thus  separated.  Such  separation  is  dialysis,  and  the  membrane 
is  called  a  dialyzing  membrane.  In  the  digestive  tube  the  mucous 
membrane  represents  the  dialyzing  membrane  with  blood  or  lymph  on 
one  side,  and  the  contents  of  the  digestive  tube  on  the  other.  Soluble 
materials,  such  as  peptones,  sugars,  etc.,  pass  through  the  mucous 
membrane  into  the  blood. 

Absorption  a  Vital  Process.  — "The  process  of  osmosis, 
and  to  a  lesser  extent  of  filtration  and  imbibition,  as  they 
are  known  to  occur  outside  the  body,  were  supposed  to 
account  for  the  absorption  of  all  the  soluble  products. 
This  belief  has  now  given  way,  in  large  part,  to  newer 
views,  according  to  which  the  living  epithelial  cells  take 
an  active  part  in  absorption,  acting  under  laws  peculiar  to 
them  as  living  substances,  and  different  from  the  laws  of 
diffusion,  filtration,  etc.,  established  for  dead  membranes. 


ABSORPTION— DIGESTION  COMPLETED. 


183 


"  Unlike  sugars  and  peptones,  fats  are  absorbed  chiefly 
in  a  solid  form  —  that  is,  in  an  emulsified  condition. 
There  can  be  no  question,  in  this  case,  of  osmosis.  It  has 
been  shown  by  nearly  all  recent  work  that  the  immediate 
agents  in  the  absorption  of  fats  are  again  the  epithelial 
cells  of  the  villi  of  the  small  intestine.  The  fat  droplets 


Right  Lymph  Vein    .... 


Junction  of  Thoracic 
Duct  with  Left  Sub- 
clavian  Vein 


Main  Lymph  Vein 
(Thoracic  Duct) 


—  Intestine 


.Lymphatic  Glands 


Fig,  66.     Lymph  Veins  — Lymphatics.     (Ventral  View.) 


are  taken  up  by  these  cells,  and  can  be  seen  microscopically 
after  digestion  in  the  act  of  passing,  or  rather  of  being 
passed,  through  the  cell  substance.  The  epithelial  cells, 
in  other  words,  ingest  the  fat  particles  lying  against  their 


1 84 


PHYSIOLOGY. 


free  ends,  and  then  pass  them  slowly  through  their  cyto- 
plasm into  the  substance  of  the  villus."  -  -  H DWELL. 

The  Lacteals  and  Lymphatics. — While  the  main  work 
of  the  lymphatics,  as  we  have  seen,  is  the  carrying  of 
lymph  from  the  tissues  of  the  body  generally  to  empty  into 
the  veins  of  the  neck,  the  lymphatics  of  the  intestines 
have  another  important  function.  They  absorb  and  carry 
the  fatty  portions  of  the  digested  food  into  the  general 
circulation.  During  most  of  the  time  the  thoracic  duct 
and  the  lymphatics  of  the  intestines  would  hardly  be 
noticed  because  they  are  filled  with  the  clear  lymph.  But 
after  absorption  of  fatty  matter  they  are  filled  with  a  white 
liquid,  called  chyle,  and  are  easily  seen. 

To  show  the  Thoracic  Duct  and  Lacteals.  —  To  show  the  thoracic 
duct  feed  a  kitten  or  puppy  on  rich  milk,  and  after  two  or  three  hours 
kill  it  as  directed  on  page  27.  As  soon  as  you  are  sure  it  is  dead, 


Lacteal  with  Valves         Capillaries  Muscles  Epithelium 

Fig.  67.     Elements  entering  into  the  Structure  of  a  Villus. 

open  the  abdominal  cavity  and  spread  out  the  mesentery.  The  white 
lacteals,  filled  with  chyle,  will  be  seen  radiating  through  the  mesentery. 
Press  on  some  of  these,  and  it  will  be  seen  that  they  are  thin  tubes 
filled  with  a  white  liquid.  They  converge  toward  the  place  of  attach- 
ment of  the  mesentery  to  the  dorsal  part  of  the  abdomen.  On  the 
dorsal  wall  of  the  abdomen,  just  posterior  to  the  diaphragm,  the  recep- 


ABSORPTION— DIGESTION  COMPLETED.          185 

tacle  of  the  chyle,  or  the  beginning  of  the  main  lymph  vein  (thoracic 
duct),  should  be  found.  Trace  it  anteriorly  through  the  chest  along- 
side the  aorta  to  its  mouth,  near  the  junction  of  the  left  subclavian  and 
jugular  veins. 

Action  of  the  Villi.  —  In  each  villus  there  are  plain 
muscle  fibers.  When  these  shorten  they  squeeze  the 
chyle,  that  has  already  been  absorbed,  into  the  lymph 
tubes  of  the  wall  of  the  intestines,  and  on  into  the  main 


Epithelial  Covering 


Lacteal 

Longitudinal  Mus- 
cular Fibers   \ 
Capillary  Network 


Fig.  68.     Intestinal  Villus. 


lymph  duct.  The  chyle  cannot  return  to  the  lacteal  when 
the  muscles  relax,  on  account  of  the  valves,  similar  to 
those  of  the  veins,  in  the  lacteal  at  the  base  of  the  villus. 
Then,  when  the  muscles  relax,  the  lacteal  is  empty,  and 
ready  to  absorb  more  of  the  emulsified  fat  that  we  call 
chyle. 

Review  of  the  Digestive  Tube.  —  The  whole  digestive 
tube  may  be  briefly  and  roughly  described  as  a  muscular 
tube  of  varying  diameter,  lined  by  mucous  membrane. 
The  muscular  coat  propels  the  contents  and  mixes  them 
with  liquids ;  the  mucous  coat  is  beset  with  glands,  making 
liquids,  some  of  which  merely  soak  the  food,  others  act 
on  it  chemically,  while  mucus  serves  to  lubricate  the  sur- 
face. It  seems  that  these  myriads  of  simple  glands  are 
not  enough,  so  several  large  compound  glands  lie  along- 
side the  food  tube  and  empty  their  secretions  into  it  by 


1 86 


PHYSIOLOGY. 


ducts ;  these  supplementary  glands  are  the  salivary  glands, 
the  pancreas,  and  the  liver. 

Length  of  the  Intestine.  —  The  length  of  the  small 
intestine  is  about  twenty-five  feet,  and  of  the  large  intestine 


Parotid  Sali- 
vary Gland 

Gullet 


Precaval  Vein 
Postcaval  Vein 


Sublingual 
Salivary  Gland 


Submaxillary 
Salivary  Gland 


Hepatic  Vein--, 


Mesenteric 
Vein 


Pancreas  and 

Duct 

Receptacle  of 

Chyle 
:nl_acteals 

Mesentery 


Intestine 
Fig.  69.    Diagram  of  the  Organs  concerned  in  the  Conversion  of  Food  into  Blood. 

five  or  six  feet.  The  large  intestine  is  not  a  direct  con- 
tinuation of  the  small;  that  is,  the  small  intestine  opens 
at  a  right  angle  into  the  large  near  the  beginning  of  the 
latter,  so  that  there  is  a  short  blind  end  called  the  cecum. 


ABSORPTION—  DIGESTION  COMPLETED. 


I87 


In  some  animals  this  is  large  and  has  considerable  length, 
but  in  man  it  is  very  short.  It  seems  to  have  been  longer 
in  man's  ancestors,  for  there  is  a  closed  prolongation  of 
the  cecum,  the  vermiform  appendix.  This  appendix  is 
frequently  the  seat  of  serious  or  fatal  inflammation,  called 
appendicitis. 


PARTS 
OF 
DIGESTIVE 
TUBE. 

MECHANI- 
CAL PRO- 
CESSES. 

GLANDS. 

LIQ- 
UIDS. 

CHEMICAL 
CHANGE. 

ABSORPTION. 

MATERIAL 

BY 

MOUTH. 

Cutting 
and 
Grinding. 

Salivary. 

Saliva. 

Starch 
to 
Sugar. 

PHARYNX. 

Raising  Soft 
Palate. 
Depressing 
Epiglottis. 

GULLET. 

Food  carried 
to  Stomach. 

Mucous. 

Mucus. 

STOMACH. 

Churning 
and 
Mixing. 

Gastric. 

Gastric 
Juice. 

Proteid 
to 
Peptone. 

Water.       1 
Salts.         1 
Sugars.      j 
Peptones,  j 

Blood 
Capillaries. 

SMALL 
INTESTINE. 

Mixing 
and 
Moving 
Food, 

Liver. 
Pancreas. 

Intestinal. 

Bile. 
Pancreatic 
Juice. 
Intestinal 
Juice. 

f  Starch  to  Sugar. 
J  Proteid  to  Peptone. 
1  Fat    ^  Emulsified. 
[          i  Decomposed. 

Water.       "I 
Salts.          1 
Sugar.        [ 
Peptone.  J 
Fats. 

Blood 
Capillaries 

Lacteals. 

LARGE 
INTESTINE. 

Food 
Forced  on. 

Mucous. 

Mucus. 

Water. 

Fig.  70.     Outline  of  Digestion. 


The  Colon.  —  The  small  intestine  joins  the  large  near 
the  lower  right  side  of  the  abdomen.  The  main  part  of 
the  large  intestine  is  called  the  colon.  It  runs  upward 
(ascending  colon),  crosses  over  to  the  left  side  (transverse 


1 88  PHYSIOLOGY. 

colon),  and  descends  the  left  side  (descending  colon),  and, 
after  curving  somewhat  like  a  letter  S  (sigmoid  flexure), 
terminates  in  the  rectum.  It  is  well  to  know  the  course  of 
the  lower  bowel,  as  pressure  may  be  so  applied  as  to  push 
the  contents  along  in  case  the  bowels  become  torpid. 

The  Work  of  the  Large  Intestine.  —  Most  of  the  ab- 
sorption is  accomplished  in  the  small  intestine ;  but  as  the 
food  passes  on  into  the  large  intestine  the  work  of  digestion 
and  of  absorption  are  carried  somewhat  farther.  If  the 
residue  be  not  soon  expelled,  there  may  be  absorption  of 
some  of  the  results  of  putrefactive  changes,  and  a  sort  of 
general  poisoning  of  the  whole  body.  Hence  the  great 
importance  of  regularly  and  thoroughly  emptying  the 
lower  bowel.  The  matter  thus  expelled  is  largely  made 
up  of  indigestible  material,  with  some  real  waste  substances. 

Taking  up  again  our  comparison  of  the  body  and  a 
furnace,  we  see  that  the  feces  are  not  true  waste  products, 
but  are  rather  clinkers,  or  material  that  has  not  been 
burned  or  oxidized  in  the  body.  The  real  wastes  of  the 
body  are  the  carbon  dioxid,  urea,  water,  etc.,  that  are 
thrown  off  by  the  lungs,  kidneys,  and  skin. 

Constipation.  —  This  is  a  very  common  disorder,  and  the  evils  at- 
tendant upon  it  are  many.  Of  course,  if  any  trouble  is  long  continued 
or  severe,  a  physician  should  be  consulted.  But  it  is  well  known  that 
certain  foods  tend  to  bring  on  such  a  condition,  and  that  other  foods 
have  the  opposite  tendency.  Thus,  cracked  wheat  and  oatmeal  are 
generally  considered  as  somewhat  laxative  in  their  effects.  The  fruits 
generally  are  laxative.  The  coarse  particles  of  graham  flour,  are  irri- 
tating to  the  mucous  lining  of  the  stomach  and  intestines,  and  for  many 
persons  serve  well  to  stimulate  the  action  of  the  bowels.  But  in  many 
persons  the  mucous  coat  is  so  sensitive  that  it  cannot  bear  such  irrita- 
tion. For  these  the  "  entire  wheat  flour  "  may  serve  the  same  purpose. 
Of  course  each  person  finds  out  by  his  own  experience  what  is  best  for 
him,  and  no  rules  can  be  laid  down  that  will  apply  to  all  cases.  But  it 


ABSORPTION— DIGESTION  COMPLETED. 


189 


may  be  well  to  know  what  is  the  usual  effect  of  some  of  the  common 
articles  of  food,  as  perhaps  some  persons  may  habitually  partake  of  cer- 
tain articles  and  do  not  suspect  that  they  are  the  cause  of  the  trouble. 
The  following  list  is  taken  from  StockhanVs  Tokology;  — 


LAXATIVE. 
Rolled  and  cracked  wheat  bread, 

gems,  biscuit,  griddlecakes. 
Crackers  and  mush  from  flour  of 

the   entire   wheat   and  graham 

flour. 
Granula. 

Bran  gruel  and  jelly. 
Fruit  puddings. 
Fruit  pies. 
All    fresh    acid    fruits,   including 

tropical     fruits,    like     bananas, 

oranges,  lemons,  etc. 
Dried  fruits. 
French     prunes     and     prunellas, 

eaten  raw. 
Stewed    dried    fruits     containing 

hydrocyanic     acid,     of     which 

peaches,  plums,  and  prunes  are 

the  best. 

New  Orleans  molasses. 
Rhubarb. 
Onions. 
Celery. 
Tomatoes. 
Cabbage,  raw. 
Corn. 
Squash. 
Cauliflower. 
Green  peas. 
Spinach. 
Beets,  .etc. 
Liver. 
Oysters. 
Wild  game. 


CONSTIPATING. 

Hot  bread. 

White  bread. 

White  crackers. 

Black  pepper  and  spices. 

Pastry  made  of  white  flour  and 
lard. 

Bread,  rolls,  dumplings,  etc.,  made 
with  baking  powder. 

Cake. 

All  custard  puddings. 

Salted  meats. 

Salted  fish. 

Dried  meats. 

Dried  fish. 

Smoked  meats. 

Poultry. 

Cheese. 

Chocolate. 

Cocoa. 

Boiled  milk. 

Tea. 

Coffee. 

Coffee  made  of  wheat,  corn,  bar- 
ley, toast,  etc. 

Beans  (dried). 

Potatoes. 

Farina. 

Sago. 

Starch. 

Tapioca. 

Rice. 

Raspberries. 

Blackberries. 


1 90  PHYSIOLOGY. 

Hygiene  of  Digestion.  —  A  prime  requisite  for  a  good 
digestion  is  a  tranquil  condition  of  the  whole  body, 
especially  of  the  nervous  system.  We  see  that  the  blood 
must  be  massed  in  the  digestive  organs  at  the  time  of 
digestion.  As  there  is  a  limited  amount  of  blood  in  the 
body,  it  is  evident  that  if  more  is  sent  to  one  part,  other 
parts  must  at  the  time  receive  less.  If  we  try  to  study 
hard  immediately  after  eating,  we  are  calling  the  blood 
away  from  the  organs  of  digestion,  and  to  that  extent  in- 
terfering with  the  process  of  digestion.  If  we  exercise 
the  muscles  too  vigorously  soon  after  eating,  we  call  the 
blood  to  the  muscles,  and  so  call  it  away  from  the  stomach 
and  intestines.  If,  after  prolonged  study,  one  is  unable  to 
obtain  sleep,  it  may  sometimes  be  efficacious  and  very  de- 
sirable to  eat  a  little  of  some  very  simple  food  for  the  pur- 
pose of  drawing  off  the  blood  to  the  stomach,  and  thus 
relieving  the  brain.  A  little  muscular  exercise  may  ac- 
complish the  same  result,  or  a  footbath  may  be  employed. 
For  many  persons  it  would  probably  be  better  to  take  a 
simple  lunch  than  to  go  to  bed  hungry,  although  one 
should  be  careful  not  to  abuse  the  stomach. 

It  is  exceedingly  difficult  to  lay  down  general  rules  in 
regard  to  diet.  To  a  certain  extent  each  person  must  be 
a  law  unto  himself,  for  what  agrees  well  with  one  may  act 
almost  as  a  poison  to  another.  Moderation  should  always 
be  observed,  especially  in  taking  foods  to  which  we  are 
not  accustomed. 

Solid  Foods  digest  Slowly.  —  Suppose  one  were  to  sit 
down  to  eat  dinner  when  ravenously  hungry.  If  in  such  a 
condition  one  begins  with  solid  food,  he  is  likely  to  eat  too 
fast.  Hunger  is  a  demand  of  the  system  for  food.  It 
takes  some  time  for  solid  food  to  go  through  all  the  pro- 


ABSORPTION—  DIGESTION  COMPLETED.          1 9 1 

cesses  of  digestion,  and  be  absorbed  into  the  system  and 
appease  hunger. 

Value  of  Soup.  —  But  if  a  soup  be  first  taken,  which  is 
readily  absorbed,  the  demand  of  the  system  will  begin  to 
be  met,  and  there  will  not  be  the  same  tendency  to  rapid 
eating.  Further,  a  warm  soup  stimulates  the  blood  flow 
in  the  mucous  membrane,  and  thus  prepares  for  more 
thorough  digestion.  It  is  more  easy  after  a  soup  to 
deliberately  masticate  the  solid  portion  of  a  meal. 

Desserts. —  Dessert  and  sweatmeats,  following  a  meal, 
are  often  very  helpful  by  further  stimulating  the  secretion 
of  the  glands.  Nuts,  which  are  not  very  digestible,  are 
beneficial  if  eaten  sparingly.  The  agreeable  taste  stimu- 
lates the  salivary  glands,  and  the  alkalinity  of  the  saliva 
stimulates  the  gastric  glands  to  increased  activity.  The 
same  may  be  said  of  cheese. 

"  Cheese  is  a  surly  elf, 
Digesting  all  things  but  itself.'1 

Pie.  —  The  average  pie  needs  some  extra  help  for  its 
digestion.  Donoghue,  formerly  champion  long-distance 
skater,  when  asked  if  he  dieted  in  preparation  for  a  race, 
said  he  avoided  pastry.  If  the  vigorous  digestion  of  a 
man  skating  for  hours  daily  in  zero  weather  cannot  profit- 
ably manage  pie,  how  in  the  case  of  sedentary  persons  ? 
If  pie  is  eaten,  it  should  be  masticated  with  very  great 
thoroughness.  Undoubtedly  most  persons  would  be  better 
off  if  they  did  not  eat  puddings  and  pastries.  Fruit  is 
best  taken  before  meals,  especially  before  breakfast. 

Hot  Drink  at  Meals. —  Hot  drink,  with  a  meal,  whether 
it  be  tea  or  coffee,  or  simply  hot  water,  is  usually  bene- 
ficial ;  especially  to  a  weak  digestion  when  taken  before 
meals. 


192  rHYSIOI.()(,\  . 

The  Bad  Effects  of  Imperfect  Mastication.  —  If  we 

swallow  food  before  it  is  thoroughly  ground  and  mixed 
with  the  saliva,  the  stomach  and  other  parts  of  the  diges- 
tive organs  will  require  much  more  time  to  reduce  the 
food  to  a  liquid  form.  Further,  when  eating  hastily,  we 
are  very  apt  to  eat  too  much.  Thus  we  may  give  the 
stomach  a  double  amount  of  material  to  handle,  and  the 
material  may  not  be  half  so  well  prepared  as  it  should 
be.  The  work  thus  thrown  upon  the  stomach  may  easily 
be  made  fourfold.  Of  course  the  organs  suffer,  and, 
sooner  or  later,  if  this  treatment  is  continued,  they  must 
break  down. 

Effect  of  Repose  on  Digestion.  —  Not  only  mastication, 
.but  the  whole  process  of  digestion,  goes  on  better  when 
the  body  and  mind  are  at  rest  and  in  a  peaceful  and  con- 
tented condition,  as  not  only  the  salivary  glands,  but  all 
the  glands,  are  under  the  control  of  the  nervous  system, 
and  are  greatly  influenced  by  the  condition  of  the  body. 
During  a  meal,  and  for  a  short  time  before  and  after,  all 
thoughts  of  one's  occupation,  and  especially  all  anxiety, 
should  be  absolutely  dismissed  from  the  mind.  For  those 
whose  digestion  is  not  strong,  it  is  especially  desirable  to 
secure  a  period  of  rest  after  each  meal,  taking  a  lounge 
or  easy-chair,  closing  the  eyes,  and,  as  nearly  as  possible, 
closing  the  mind ;  for  some,  even  a  short  nap  is  very 
helpful. 

Conversation  at  Meals.  —  During  a  meal  there  should 
be  conversation  on  topics  of  general  interest.  "  Chatted 
food  is  already  half  digested." 

Deliberation  in  Eating.  —  It  is  said  that  the  people  of 
the  United  States  are  nervous,  and  eat,  as  they  do  nearly 
everything,  hastily.  Deliberation  in  eating  adds  to  dignity 


ABSORPTION— DIGESTION  COMPLETED.          193 

as  well  as  health,   and  properly  may  be  considered  an 
evidence  of  culture. 

Time  of  Eating.  —  Probably  our  almost  universal  custom 
of  three  meals  a  day,  resulting  from  experience,  is  well 
adapted  to  the  needs  of  our  people.  Theoretically  the 
chief  meal  should  be  near  the  middle  of  the  day,  as  is  the 
custom  in  the  country;  for  the  bodily  powers  are  higher 
than  later  in  the  day.  But  for  city  people,  and  others  who 
are  very  busy  in  the  middle  of  the  day,  it  is  undoubtedly 
better  to  take  the  chief  meal  after  the  rush  of  the  day's 
work  is  over,  when  there  is  time  for  a  deliberate  meal  and 
when  the  mind  is  free  from  business  cares.  For  many,  too, 
this  is  the  only  time  when  the  whole  family  can  leisurely 
meet  at  the  table. 

Eating  between  Meals.  —  The  stomach  should  have 
time  to  rest  and  prepare  for  the  work  of  digesting  another 
meal.  Many  find  two  meals  a  day  sufficient.  There  are 
some  persons,  however,  for  whom  it  would  be  better  to 
have  more  meals,  with  less  food  at  each  meal.  Meals 
should  be  regular. 

Amount  of  Food  Needed.  —  This  varies  greatly  with  the 
individual,  age,  the  kind  and  amount  of  labor,  etc.,  so  that 
no  very  helpful  rule  can  be  given.  Each  person  must  find 
by  experience  what  is  best  for  himself.  It  is  the  opinion 
of  many  leading  physicians  that  the  majority  of  man- 
kind eat  too  much.  The  fasting  enjoined  upon  some  is 
undoubtedly  hygienic ;  and  it  would  be  a  valuable  lesson 
for  more  persons  to  experiment  in  the  line  of  fasting. 

Errors  of  Diet.  —  Sir  Henry  Thompson,  one  of  the 
foremost  authorities  in  the  world  on  the  subject  of  foods, 
says :  "  I  have  come  to  the  conclusion  that  more  than  half 


194  PHYSIOLOGY. 

of  the  disease  which  embitters  the  middle  and  latter  part 
of  life  is  due  to  avoidable  errors  of  diet ;  and  that  more 
mischief,  in  the  form  of  actual  disease,  of  impaired  vigor, 
and  of  shortened  life,  accrues  to  civilized  man  from 
erroneous  habits  of  eating  than  from  the  habitual  use  of 
alcoholic  drink,  considerable  as  I  know  that  evil  to  be." 

READING.  —  Disorders  of  Digestion,  Brunton  ;  Indiges- 
tion and  Biliousness,  Fothergill ;  A  Plea  for  a  Simpler 
Life,  Keith. 

Summary. —  i.  The  hairlike  villi  lining  the  small  intestine  absorb 
the  liquefied  food. 

2.  Sugars  and  peptones  are  carried  away  by  the  blood  capillaries 
and  pass  through  the  Tiver,  but  the  fats  are  taken  by  the  lacteals  into 
the  lymph  stream  to  join  the  blood  in  the  subclavian  vein. 

3.  Digestion  is  greatly  influenced  by  the  condition  of  the  nervous 
system. 

4.  Mastication  should  be  thorough. 

5.  Chat  at  meals  is  hygienic. 

6.  Rest  after  meals. 

7.  Soups  and  desserts  have  a  physiological  justification,  though  the 
latter  often  become  harmful. 

8.  There  is  a  great  amount  of  suffering  from  intemperance  in  eating 
as  well  as  in  drinking. 

Questions.  —  I .    What  foods  are  absorbed  most  quickly  ? 

2.  Is  appendicitis  more  common  than  formerly  ? 

3.  What  is  the  meaning  of  "  laugh  and  grow  fat  "  ? 


CHAPTER   XII. 
NUTRITION. 

Ledger  Account  of  the  Body  and  its  Organs.  —  Through 
the  digestive  tube  and  lungs  the  body  receives  additions, 
and  there  is  a  corresponding  loss  through  the  lungs,  skin, 
kidneys,  and  intestines.  So  a  ledger  account  might  be 
kept  with  the  body,  and  it  should  balance  in  the  long  run, 
since  in  adult  life  the  weight  remains  practically  constant. 

So  we  might  take  a  single  organ,  say  the  liver,  and 
balance  its  accounts.  It  receives  a  large  amount  of  blood. 
To  offset  what  it  takes  from  the  blood,  it  gives  to  the 
intestines  a  large  quantity  of  bile,  and  to  the  blood  it  gives 
glycogen. 

It  is  especially  interesting  to  note  the  losses  and  gains 
of  the  blood  as  it  passes  through  the  various  organs  of  the 
body.  A  river,  flowing  past  one  State  after  another,  will 
take  some  of  the  soil  of  each  and  deposit  some  of  its 
muddy  particles  on  the  banks  of  each  State.  Of  course, 
the  blood  is  unlike  the  river,  in  that  it  empties  into  itself ; 
i.e.  it  is  truly  a  circulation.  The  blood  takes  something 
from,  and  gives  something  to,  each  organ  as  it  flows 
through  it.  From  the  intestine  the  blood  gets  the  chief 
part  of  its  new  material  in  the  newly  digested  food.  To 
the  muscles  the  blood  gives  nutritive  material  and  oxygen, 
and  receives  water,  carbon  dioxid,  and  other  waste  matters. 
The  account  would  be  similar  with  the  brain.  In  the  skin 
and  the  kidneys  the  blood  has  great  losses  and  little  gains. 


196 


PHYSIOLOGY. 


The  accompanying  diagrams  may  help  in  presenting 
the  main  points  in  the  blood  circuit,  and  the  losses  and 
gains  in  its  course. 

Blood  a  Mixture  of  Good  and  Bad.  —  In  the  common 
blood  streams  are  combined  the  good  and  the  bad.  The 

Capillaries 


Vein 


Artery 


Artery 


Vein 


Capillaries 
Fig.  71.    Diagram  of  the  Heart  and  Blood  Tubes  (Dorsal  View). 

newly  digested  food  is  received  into  a  current  of  impure 
blood  in  the  postcaval  vein.  The  blood  from  the  kidneys, 
probably  the  purest  blood  in  the  body,  joins  the  same 
impure  stream.  From  the  aorta,  red  blood,  usually  called 


NUTRITION. 


197 


pure  —  the  same  kind  that  goes  to  the  brain  —  is  sent 
to  the  kidneys  and  to  the  skin  to  be  purified.  Yet,  as  this 
mixed  blood  flows  through  each  organ,  that  organ,  so  long 
as  it  is  in  health,  takes  from  it  only  what  it  should  take. 


Lung  Capillaric 


Pulmonary  Vein 

Left  Auricle-- 
Left Ventricle- 


Body  Capillaries 

Fig.  72.    Diagram  of  the  Circulation,  representing  the  Right  and  Left  Halves  separated 
(as  they  are  in  reality),  showing  that  the  Blood  makes  but  One  Circuit. 

Action  of  Diseased  Kidneys.  —  The  kidney  takes, 
during  health,  only  the  waste  matters,  leaving  the  valuable 
nourishing  material.  But,  in  disease,  the  kidneys  may 


198 


PHYSIOLOGY. 

LUNG 


PULMONARY  VEIN 
LEFT  AURICLE 


LEFT  VENTRICLE 


PULMONARY  ARTERY 

RIGHT  VENTRICLE 

RIGHT  AURICLE 


Fig.  73.    Diagram  of  the  Circulation  of  the  Blood. 


NUTRITION.  199 

take  out  some  of  the  most  valuable  portions  of  the  nutri- 
ment. Suppose  that  in  a  mill,  a  workman,  whose  business 
is  to  shovel  out  wastes,  becomes  crazy,  and  shovels  wheat 
or  flour  out  of  the  mill  into  the  stream  below.  The  dis- 
eased kidney  may  be  said  to  have  become  crazy,  and  in 
the  disease  called  "diabetes"  throws  out  sugar,  and  in 
"  albuminuria  "  excretes  albumen. 

Blood  Streams  like  Water  Pipes  and  Sewer  Combined. 

—  It  is  as  though  the  water  supply  of  a  city  house  was  taken 
from  the  sewer ;  each  organ  needing  a  supply  of  building 
material  acts  like  a  filter,  taking  from  the  blood  what  it 
needs,  paying  no  attention  to  the  impurities  present,  and  the 
organs  of  excretion  select  the  impurities,  allowing  the  useful 
substances  to  pass  on  to  the  places  where  they  are  needed. 

A  Living  Eddy.  —  Huxley  has  very  aptly  compared  the 
body  to  an  eddy,  whose  form  remains  the  same,  but  whose 
particles  are  ever  changing. 

"  To  put  the  matter  in  the  most  general  shape,  the  body 
of  the  organism  is  a  sort  of  focus  to  which  certain  material 
particles  converge,  in  which  they  move  for  a  time,  and 
from  which  they  are  expelled  in  new  combinations. 

"  The  parallel  between  a  whirlpool  in  a  stream  and  a 
living  being,  which  has  often  been  drawn,  is  as  just  as 
it  is  striking.  The  whirlpool  is  permanent,  but  the  par- 
ticles of  water  which  constitute  it  are  incessantly  changing. 
Those  which  enter  it  on  the  one  side  are  whirled  around 
and  temporarily  constitute  a  part  of  its  individuality;  as 
they  leave  it  on  the  other  side,  their  places  are  made  good 
by  new  comers. 

"  Those  who  have  seen  the  wonderful  whirlpool,  three 
miles  below  the  Falls  of  Niagara,  will  not  have  forgotten 
the  heaped-up  wave  which  tumbles  and  tosses,  a  very 


200  PHYSIOLOGY. 

embodiment  of  restless  energy,  where  the  swift  stream 
hurrying  from  the  falls  is  compelled  to  make  a  sudden 
turn  toward  Lake  Ontario. 

"  However  changeful  in  the  contour  of  its  crest,  this 
wave  has  been  visible,  approximately  in  the  same  place 
and  with  the  same  general  form,  for  centuries  past.  Seen 
from  a  mile  off,  it  would  appear  to  be  a  stationary  hillock 
of  water.  Viewed  closely,  it  is  a  typical  expression  of  the 
conflicting  impulses  generated  by  a  swift  rush  of  material 
particles. 

"  Now,  with  all  our  appliances,  we  cannot  get  within 
a  good  many  miles,  so  to  speak,  of  the  living  organism. 
If  we  could,  we  should  see  that  it  was  nothing  but  the 
constant  form  of  a  similar  turmoil  of  material  molecules, 
which  are  constantly  flowing  into  the  organism  on  the 
one  side  and  streaming  out  on  the  other." 

Importance  of  Renewal  of  Blood  and  Lymph.  —  It 

will  be  well  here  to  recall  some  facts  noted  in  connection 
with  the  study  of  the  blood  and  lymph.  We  then  learned 
that  the  lymph  (the  supply  and  renewal  of  which  depends 
upon  the  blood)  surrounds  the  individual  cells  which  make 
up  the  tissues  of  the  body ;  and  that,  to  a  certain  extent, 
every  cell  lives  an  independent  life,  each  taking  its  nourish- 
ment directly  from  the  lymph  around  it.  The  importance 
of  an  abundant  supply  of  good  lymph  is  now  more  ap- 
parent. If  digestion  is  not  good,  or  the  food  be  insufficient 
or  of  poor  quality  (whether  naturally  or  from  being  badly 
cooked),  good  blood  cannot  be  made,  and  the  lymph  will 
not  be  good.  The  cells  are  more  or  less  starved,  or 
poisoned  if  wastes  are  not  properly  removed,  and  the  gen- 
eral tone  of  the  body  will  soon  be  lowered ;  for  the  health 
of  the  body  as  a  whole  depends  on  the  average  condition 


NUTRITION.  201 

of  the  cells  composing  the  body,  just  as  the  condition  of 
any  community  depends  on  the  average  condition  of  the 
individuals  of  that  community. 

Fat  as  a  Tissue.  —  As  a  tissue  fat  serves  as  a  stored-up 
food.'  The  camel's  hump  is  a  well-known  instance.  In 
some  of  the  savage  races  fat  is  stored  in  a  very  similar 
hump.  But  in  most  persons  it  is  distributed  more  evenly 
over  the  body,  though  there  is  a  tendency  to  deposit  rather 
more  over  the  abdomen.  A  fat  person  can  endure  starva- 
tion longer,  other  things  being  equal,  than  a  thin  person. 
A  layer  of  fat  under  the  skin  serves  also  as  a  heat  saver. 

Hibernation.  —  Hibernating  animals  are  fat  when  they  enter  upon 
their  winter  sleep,  but  are  lean  when  they  come  out  in  the  spring. 
Remaining  inactive  they  have  produced  very  little  energy,  their  only 
motions  being  a  slow  and  feeble  breathing  and  a  correspondingly 
reduced  heart  beat.  They  have  consumed  the  fat,  using  it  mainly  in 
maintaining  the  necessary  heat.  In  short,  they  have  burned  their  fat 
to  keep  them  warm. 

The  Hibernation  of  a  Bear.  —  In 'one  of  Captain  Mayne  Reid's 
stories  (The  Plant  Hunters}  we  are  told  how  the  hunters  followed  a 
bear  into  a  cave.  At  the  innermost  end  of  this  very  long  cave  they 
finally  killed  the  bear.  Just  at  this  time  they  find  that  their  candles 
are  all  burned  out,  and  they  are  left  in  complete  darkness,  lost  in  the 
bowels  of  the  earth.  Failing  to  grope  their  way  out,  they  are  at  last 
driven  to  this  expedient :  With  what  combustibles  they  can  gather 
together,  including  their  gunstocks  and  some  of  the  fat  of  the  bear, 
they  melt  some  of  the  fat,  they  use  the  gun  barrels  for  molds,  take 
strips  of  their  clothing  for  wicks,  and  make  two  long  candles.  With 
these  they  finally  light  their  way  out  to  the  upper  world. 

Respiration  and  Oxidation  of  Candle.  —  Now  we  have  seen  that 
when  we  burn  a  tallow  candle  one  of  the  chief  products  of  the  combus- 
tion is  carbon  dioxid.  Another  product  of  the  burning  is  common 
water.  If,  then,  these  hunters  had  left  this  bear  to  his  winter's  nap,  he 
would  have  consumed  this  fat  in  the  slow  process  of  breathing,  and 
it  would  have  given  off  the  same  products,  as  we  have  proved  that  two 
of  the  waste  matters  of  the  expired  breath  are  carbon  dioxid  and  water. 


202  PHYSIOLOGY. 

Glycogen. — As  stated  above,  glycogen  is  formed  in  the 
liver.  This  is  indicated  by  the  fact  that  there  is  more 
sugar  in  the  blood  in  the  hepatic  vein  than  in  the  portal 
vein,  except  during  digestion.  Glycogen  is  formed  by  and 
stored  in  the  liver,  and  is  doled  out  to  the  tissues.  That 
muscles  use  sugar  in  their  action  is  indicated  in  the  fact 
that  the  arteries  bring  to  the  muscles  more  sugar  than  is 
carried  away  from  them  by  the  veins.  As  fat  is  a  reserve 
food,  so  glycogen  serves  as  a  temporary  carbohydrate  re- 
serve. 

Nutrition.  —  All  the  changes  that  take  place  between 
the  reception  of  food  and  the  excretion  of  waste  are 


ANIMAL 
PROTOPLASM 


INORGANIC  WORLD 

Fig.  74.    Animal  and  Vegetable  Protoplasm. 

included  under  the  term  nutrition.  The  materials  taken 
as  food  are  usually  more  complex  and  unstable,  the  waste 
products  more  simple  and  stable ;  just  as  the  products  of 
combustion  are,  as  a  rule,  simpler  and  more  stable  than 
fuels.  In  both  combustion  and  the  processes  of  nutrition 
the  final  result  is  oxidation,  more  or  less  direct. 

Muscular  Exertion  and  Excretion  of  Urea.  —  Since 
muscles  are  the  engines  of  motion,  and  also  are  largely 
composed  of  proteid  (nitrogen-containing)  material,  we 
would  naturally  expect  that  increased  muscular  exertion 
would  increase  the  excretion  of  urea  (the  only  nitrogen- 


NUTRITION. 


203 


containing  waste).  But  experiment  shows  that  increased 
muscular  action,  such  as  mountain  climbing,  hardly  in- 
creases the  amount  of  urea  excreted.  Such  work,  how- 
ever, does  largely  increase  the  amount  of  carbon  dioxid 
excreted.  It  is  thought,  therefore,  that  our  energy  is 
largely  derived  from  carbohydrate  foods  and  fats,  and  this 
view  is  strengthened  by  the  fact  that  our  beasts  of  burden 
depend  chiefly  on  carbohydrate  foods. 


ASSIMILATION^, 
CIRCULVTION, 

ABSORPTION^ 
DIGESTION 


VEGETABLE  FOOD 


INORGANIC  (MINERAL)  MATTER 

Fig.  75.     Life  Processes. 

While  increased  muscular  action  does  not  very  per- 
ceptibly increase  the  amount  of  urea  excreted,  an  addition 
to  the  amount  of  proteid  food  taken  does  increase  the 
amount  of  urea. 

Metabolism.  —  The  building-up  or  constructive  pro- 
cesses are  included  under  anabolism,  while  katabolism 
designates  the  tearing  down  or  destructive  processes.  All 
the  processes  of  nutrition,  both  of  building  up  and  tearing 
down,  are  included  in  the  term  metabolism. 

The  Indestructibility  of  Matter.  —  We  are  agreed  that 
we  cannot  destroy  matter.  We  may  demolish  a  house,  but 
the  material  is  all  there.  We  may  burn  it,  but  if  we  could 
gather  the  ashes  and  that  part  of  the  smoke  and  gases 


204  PHYSIOLOGY. 

furnished  by  the  material  of  the  house,  the  weight  would 
all  be  recovered. 

In  the  continual  wasting  away  of  our  bodies  there  is  no 
real  loss  of  matter.  Our  weight  is  reduced,  but  the  wastes 
are  still  part  of  the  earth  or  air,  and  are  used  again.  For 
instance,  a  particle  of  carbon  in  the  carbon  dioxid  of  the 
expired  breath  may  be  taken  in  through  a  blade  of  grass  in 
an  adjoining  field.  A  cow  may  eat  the  grass,  and  we  may 
soon  take  the  very  same  particle  of  carbon  in  the  flesh  or 
milk  of  the  cow.  Or  the  carbon  may  be  taken  by  that 
kind  of  grass  called  wheat,  and  become  part  of  the  seed 
or  grain  of  wheat,  and  be  made  into  flour  and  be  eaten  as 
bread,  and  be  part  of  us  once  more.  Or  this  particle  of 
carbon  might  be  carried  by  the  winds  to  Florida  or  Cali- 
fornia, and  become  part  of  an  orange,  and  come  again  to 
make  part  of  our  bodies.  Thus  there  is  a  ceaseless  round 
of  matter  into  and  out  of  our  bodies.  The  plants  furnish 
food  for  us,  and  we  help  to  make  food  for  them  by  the 
wastes  of  our  substance.  No  one  has  a  monopoly  of  any 
portion  of  matter ;  it  is  now  ours,  now  some  one  else's.  A 
particle  may  pass  from  one  animal  to  another  animal,  as 
when  we  eat  flesh  or  other  animal  food.  But  more  often 
the  wastes  of  our  bodies  go  to  make  part  of  the  air  or  the 
soil,  and  are  then  taken  by  some  plant  before  again  becom- 
ing part  of  our  tissues.  But  we  are  as  unable  to  destroy 
matter  as  we  are  to  create  it. 

The  Indestructibility  of  Force.  —  So  with  energy.  We 
cannot  create  it  and  we  cannot  destroy  it.  We  derive  our 
energy  from  the  food  we  eat.  And  this  food  we  get 
directly  or  indirectly  from  the  vegetable  kingdom. 

An  engine  gets  energy  from  the  combustion  of  fuel.  In 
the  growth  of  the  plant  under  the  influence  of  sunlight  the 


NUTRITION. 


2O5 


plant  has  stored  energy.  Now  that  the  wood  or  coal  are 
burned  the  energy  is  given  out,  primarily  as  heat.  But  we 
may  convert  the  heat  into  electricity,  the  electricity  into 
light,  or  back  again  into  heat  if  we  wish.  We  get  our 
energy  from  food  as  the  engine  gets  its  energy  from  fuel. 
This  is  saying  nothing  against  the  superiority  of  the 
human  body,  and  is  not  in  the  least  degrading.  We  are 


c  o 


N    H 


ANIMALS 

AND  PLANTS  NOT 

POSSESSING  CHLOROPHYLL, 

WHICH  DISINTEGRATE 
COMPLEX  CHEMICAL  COM- 
POUNDS,  LIBERATING 
ENERGY  IN  THE 

PROCESS! 


PLANTS 
POSSESSING  CHLOROPHYLL 

INTEGRATE  COMPLEX 

CHEMICAL  COMPOUNDS, 

STORING  UP  SOLAR  ENERGY 

IN  THE  PROCESS, 

THEY 


N   H. 


Solar  Energy 


Energy  originally  obtained  from  the  sun  radiated 
by  the  animal  (chiefly)  into  space  as  heat,  and 
thereby  becoming  ultimately  unavailable 


Fig-  76.    Relation  of  Plants  and  Animals. 

self-maintaining,  self-directing,  growing,  living  machines. 
Still,  starvation  soon  puts  an  end  to  our  ability  to  produce 
energy  of  any  kind. 

The  Utilization  of  Energy  in  the  Body  and  in 
Machines.  —  Now,  it  is  a  well-recognized  fact  that  in  very 
many  machines  only  the  smaller  part  of  the  energy  is 
directed  to  the  end  sought.  Take  a  common  candle.  We 
wish  to  get  light  from  it.  But  most  of  the  energy  of  the 
candle  is  devoted  to  making  heat,  which  in  this  case  we  do 
not  desire.  In  many  machines  there  is  great  loss  from 
friction,  from  radiating  heat,  etc.  Physiologists  tell  us  that 
the  human  body  utilizes  a  larger  portion  of  its  energy  than 


206  PHYSIOLOGY. 

most  machines.     While  energy  may  fail  to  be  used  for  the 
desired  purpose,  it  is  never  destroyed  nor  really  lost. 

CORRELATION  AND  CONSERVATION  OF  ENERGY. 

1.  The  Correlation  of  Energy.  —  All  kinds  of  energy 
are  so  related  to  one  another  that  energy  of  any  kind  can 
be  transformed  into  energy  of  any  other  kind. 

2.  The  Conservation  of  Energy.  —  When  one  form  of 
energy  disappears,  an   exact  equivalent  of  another  form 
of  energy  always  takes  its  place,  so  that  the  sum  total  of 
energy  is  unchanged. 

These  two  principles  constitute  the  corner  stone  of  phys- 
ical science,  and  must  be  learned  and  kept  in  mind  if  we 
would  understand  the  actions  of  our  bodies,  and  our  rela- 
tions to  the  surrounding  parts  of  the  world  and  the  universe 
in  which  we  live  and  of  which  we  must  consider  ourselves 
a  part. 

READING.  —  Foods  and  Dietaries,  Burnet ;  Diet  in  Rela- 
tion to  Age  and  Activity,  Thompson. 


Summary.  —  i .  The  blood  flow  is  a  true  circulation ;  that  is,  the 
blood  moves  in  a  circuit,  being  more  or  less  altered  by  every  organ  it 
passes  through. 

2.  The  body  is  an  eddy  into  which  particles  are  constantly  entering, 
forming  part  of  it  a  while,  and  then  passing  out. 

3.  Fat  as  tissue  is  stored  food,  and  consequently  stored  energy. 

4.  Glycogen  is  a  carbohydrate  reserve  stored  temporarily  in  the 
liver. 

5.  Nutrition  includes  all  the  processes  of  the  body  from  the  time 
matter  enters  as  food  until  it  leaves  as  waste  matter. 

6.  The  building-up  processes  of  the  body  are  called  Anabolism,  the 
tearing  down  are  Katabolism,  and  both  of  these  are  included  under 
Metabolism. 


NUTRITION.  207 

7.  We  can  create  neither  matter  nor  force,  but  are  dependent  on 
food  as  the  engine  is  dependent  on  fuel. 

8.  We  are  dependent  on  the  green  plants  for  our  food. 

9.  The  animal  body  utilizes  more  of  the  energy  contained  in  food 
than  the  engine  utilizes  from  fuel. 

Questions.  —  i.   Why  is  it  that  some  persons  eat  a  large  amount  of 
food  yet  remain  thin  ? 

2.  What  is  meant  by  "lymphatic  temperament"  ? 

3.  Classify  the  organs  shown  in  Fig.  73  according  to  their  functions. 

4.  What  animal   is    most   thoroughly  protected    from    cold  by  an 
envelope  of  fat  ? 

5.  How  are  plants  and  animals  dependent  one  on  the  other  ? 


CHAPTER   XIII. 
ALCOHOL. 

Alcohol.  —  Alcohol  is  not  a  food.  But  because  it  is 
taken  into  the  digestive  tube,  and  produces  its  effects, 
primarily,  through  the  digestive  system,  it  is  here  pre- 
sented. 

If  we  eat  a  sufficient  amount  of  bread  to-day,  we  do 
not  crave  a  larger  amount  to-morrow;  but  the  appetite 
for  alcohol  grows ;  the  law  of  its  use  is  the  law  of  in- 
crease, until  the  terrible  alcohol  habit  is  formed. 

Alcohol  and  Crime.  —  Aside  from  the  fearful  effects 
of  the  habitual  use  of  alcohol  upon  the  individual  himself, 
statistics  show  that  a  large  share  of  the  poverty  and  crime 
in  the  world  is  due  to  its  use.  Nearly  every  child  has 
known  of  the  effects  in  the  family  of  some  drunkard,  how 
the  father  is  feared,  how  all  are  ashamed  of  him,  how 
the  children  are  poorly  clothed,-  often  not  sent  to  school, 
because  not  sufficiently  supplied  with  clothes  and  books ; 
all  these,  and  the  dirt  and  misery  so  well  known  in  so 
many  cases,  are  a  sufficient  warning  not  to  make  the 
slightest  beginning  of  this  habit.  History  is  full  of  ac- 
counts of  men  who  thought  they  could  stop  when  they 
chose  ;  the  grip  of  the  alcohol  habit  is  almost  as  relentless 
as  the  grip  of  death.  There  is  one  safe  rule  :  "  Touch  not, 
taste  not,  handle  not." 

Alcohol  and  Energy.  —  Some  of  the  best  authorities 
state  that  alcohol,  taken  in  small  doses,  is  oxidized  in  the 

208 


ALCOHOL.  209 

body,  producing  energy ;  but  they  do  not  class  it  with 
foods,  nor  do  they  recommend  its  use. 

Alcohol  and  Heat.  —  As  to  its  power  to  produce  heat, 
the  fact  is  that,  as  ordinarily  taken,  alcohol  lowers  the  tem- 
perature of  the  body.  It  is  well  known  that  the  face  is 
flushed  as  the  result  of  taking  alcoholic  drink.  This  means 
that  more  blood  has  been  sent  to  the  skin.  That  sending 
of  blood  to  the  skin  gives  a  sensation  of  heat ;  we  feel  hot 
when  the  skin  is  flushed  from  other  cause,  as  some  emotion. 
But  if  the  temperature  of  the  body  be  taken  at  the  time 
when  the  body  feels  warm,  in  each  case  it  may  be  found 
that  the  temperature  is  actually  lowered ;  and  we  can  see 
the  reason  for  this,  for  the  more  blood  there  is  in  the  skin, 
the  more  heat  will  be  given  off,  and  thus  the  amount  of 
heat  in  the  body  diminished. 

Alcohol  and  Muscular  Energy.  —  Neither  does  alcohol 
as  usually  taken  increase  the  energy  of  the  body  so  far 
as  muscular  work  is  concerned.  Experience  shows  that 
men  can  endure  more  cold  and  more  hard  labor  without 
alcohol  than  with  it.  This  has  been  repeatedly  proved 
in  arctic  expeditions,  in  the  army  and  navy,  during  the 
hardships  and  exposures  of  forced  marches  and  depriva- 
tions in  all  climates. 

Danger   in   Drinking   Alcohol   in   Cold    Climates.  - 

Especially  if  one  is  to  be  exposed  to  severe  cold  is  it 
dangerous  to  take  alcoholic  drink ;  many  a  member  of 
exploring  parties  has  lost  his  life  by  disobeying  this  rule. 

Alcohol  and  Training.  —  It  is  a  significant  fact  that 
men  training  for  athletic  contests  (no  matter  what  their 
ordinary  habits  or  principles)  let  alcoholic  drinks  alone. 
One  of  the  famous  pugilists  said :  "  I'm  no  teetotaler,  but 


210  PHYSIOLOGY. 

when  I  have  business  on  hand,  there's  nothing  like  water 
and  dumb-bells." 

Alcohol  as  a  Stimulant.  —  "  Alcohol  is  a  typical  stimu- 
lant ;  it  acts  as  a  whip,  causing  a  temporary  acceleration 
of  physiological  activity.  Such  acceleration  must  subse- 
quently be  paid  for,  the  extra  expenditure  brought  about 
by  alcohol  entailing  diminished  capacity  for  further  exer- 
tion. Alcohol  is  thus  of  service  only  for  emergencies  of 
short  duration ;  it  is  eminently  harmful  when  prolonged 
exertion  and  endurance  are  required.  Like  all  rapid 
stimulants,  alcohol  is  in  large  doses  a  direct  depressant." 
—  WALLER. 

Alcohol  as  a  Narcotic.  —  Many  prefer  to  call  alcohol 
a  narcotic.  In  large  doses  it  seems  to  paralyze  the  mech- 
anism regulating  the  caliber  of  the  arteries ;  hence  the 
flushing  above  noted. 

Alcohol  and  Water.  —  Alcohol  has  a  strong  affinity  for 
water,  and  extracts  it  from  tissues.  When  we  preserve 
animal  tissue  in  alcohol,  the  alcohol  abstracts  the  water, 
thus  hardening  and  preserving  the  substance. 

Alcohol  a  Poisonous  Drug.  —  Alcohol  should  be  classed 
with  the  poisonous  drugs  (e.g.  arsenic,  chloroform,  bella- 
donna, strychnin,  etc.),  the  exact  nature  of  whose  effects 
it  is  exceedingly  difficult  to  determine.  We  do  know  that 
they  are  very  dangerous  substances ;  and  there  is  one  rule 
that  will  apply  to  them  all :  Never  use  them  except  under 
the  advice  of  a  physician. 

The  Effects  of  Drinking  Alcohol.  —  "  The  most  serious 
and  widespread  derangement  of  the  natural  taste  is  that 
caused  by  alcoholic  drinks.  Alcohol  has  been  demon- 
strated to  be  a  poison.  Its  continued  use,  even  in  what 


ALCOHOL.  211 

is  called  moderate  quantities,  will  pave  the  way  for  many 
diseases,  some  of  which  are  sure  to  overtake  those  who 
have  the  habit  of  using  drinks  with  alcohol  in  them. 

"  Examples  of  the  effect  of  the  excessive  use  of  alcoholic 
drinks  are  numerous  and  revolting  enough  in  most  com- 
munities to  make  the  strongest  appeals  against  their  use. 

"When  it  is  seen  that  by  the  use  of  alcohol  an  intelli- 
gent man  may  act  without  reason ;  that  a  kind-hearted 
man  may  become  brutal  to  his  most  loved  friends ;  that 
it  may  cause  an  honorable  man  to  become  a  dishonorable 
one  ;  that  it  may  make  a  noble  nature  become  one  with  the 
most  depraved  of  tastes ;  when  its  use  has  over  and  over 
again  been  the  cause  of  disappointment,  of  intense  suffer- 
ing, and  of  crime,  —  it  would  seem  that  vastly  stronger 
reasons  existed  against  its  use  'than  the  mere  fact  that 
some  slight  changes  in  the  tissues  occur  which  might  pos- 
sibly be  demonstrated.  It  is  to  avoid  these  serious  results 
that  the  use  of  alcohol  is  to  be  shunned,  and  not  simply 
to  avoid  a  differently  shaped  liver. 

"  The  physiological  effects  of  poisons  are  generally  much 
greater  than  the  visible  changes  which  they  produce  in 
the  tissues  would  lead  us  to  expect.  Indeed,  such  effects 
can  seldom  be  detected  by  changes  seen  in  the  tissue  cells. 

"  Strychnin  produces  powerful  spasms  which  end  in 
death.  It  acts,  it  is  said,  on  the  spinal  cord,  but  it  would 
be  hard  to  show  any  changes  that  it  produces  in  the  cells. 
And  a  knowledge  of  the  changes  it  produces  in  the  cells 
could  not  make  us  fear  the  poison  any  more  than  we  do, 
who  know  that  it  results  in  suffering  and  death."-- JENKINS. 

Temperance  Drinks.  —  Many  well-meaning  persons  use 
the  various  preparations  called  "  root  beers,"  perhaps  with- 
out realizing  that  most,  if  not  all,  contain  yeast,  and  in 


212  PHYSIOLOGY. 

their  preparation  undergo  fermentation,  producing  alcohol, 
though  not  ordinarily  in  large  amounts.  By  giving  such 
drinks  (often  called  "temperance  drinks")  to  children,  an 
appetite  for  alcohol  may  be  cultivated  and  the  beginning 
of  a  terrible  habit  made.  (And  it  may  be  well  here  to  note 
the  real  meaning  of  the  word  habit,  tJiat  which  holds  us.) 

Cider.  —  Nor  is  it  "advisable  to  keep  cider  about  a  house 
where  there  are  children.  "  It  is  perfectly  sweet,"  you 
say.  Yes,  but  unless  it  is  all  soon  consumed  it  will  fer- 
ment. It  is  unwise,  to  say  the  least,  to  put  temptation 
in  the  way  of  those  whose  habits  are  not  formed. 

STIMULANTS. 

[WILLIAM  H.  HOWELL,  Ph.D.,  M.D.,  Professor  of  Physiology,  Johns  Hopkins  University, 
American  Text-Book  of  Physiology.} 

"  The  well-known  stimulating  effect  of  alcohol,  tea, 
coffee,  etc.,  is  probably  due  to  a  specific  action  on  the 
nervous  system  whereby  the  irritability  of  the  tissue  is 
increased.  The  physiological  effect  of  tea,  coffee,  and 
chocolate  is  due  to  the  alkaloid  caffeine  (trimethyl  xanthin) 
and  theobromine  (dimethyl  xanthin).  In  small  doses  these 
substances  are  oxidized  in  the  body  and  yield  a  correspond- 
ing amount  of  energy,  but  their  value  from  this  standpoint 
is  altogether  unimportant  compared  with  their  action  as 
stimulants.  Alcohol  also,  when  not  taken  in  too  large 
quantities,  may  be  oxidized  in  the  body,  and  furnish  a  not 
inconsiderable  amount  of  energy.  It  is,  however,  a  matter 
of  controversy  at  present  whether  alcohol  in  small  doses 
can  be  considered  a  true  foodstuff,  capable  of  serving  as  a 
direct  source  of  energy,  and  of  replacing  a  corresponding 
amount  of  fats  or  of  carbohydrates  in  the  daily  diet.  The 
evidence  is  partly  for  and  partly  against  such  a  use  of  al- 


ALCOHOL.  213 

cohol.  For  example,  Reichert  finds  that  moderate  doses 
of  alcohol  given  to  a  dog  do  not  affect  the  heat  production 
of  the  body  as  measured  by  a  calorimeter.  Since  the  alco- 
hol is  completely,  or  nearly  completely,  oxidized  in  the 
body,  and  gives  off  considerable  heat  in  the  process,  the 
fact  that  the  total  heat  production  remains  unaltered  in- 
dicates that  the  oxidation  of  the  alcohol  protects  an  iso- 
dynamic  amount  of  proteid  or  non-proteid  material  in  the 
body  from  consumption,  thus  acting  as  a  foodstuff  capable 
of  replacing  other  elements  of  the  food.  On  the  contrary, 
Miura  has  arrived  at  exactly  opposite  results  in  a  series  of 
experiments  made  by  another  method.  In  these  experi- 
ments Miura  brought  himself  into  a  condition  of  nitrogen 
equilibrium  upon  a  mixed  diet.  Then  for  a  certain  period 
a  portion  of  the  carbohydrates  was  omitted  from  the  diet, 
and  its  place  substituted  by  an  isodynamic  amount  of 
alcohol.  The  result  was  a  loss  of  proteid  from  the  body, 
showing  that  the  alcohol  had  not  protected  the  proteid 
tissue  as  it  should  have  done  if  it  acts  as  a  food.  In  a 
third  period  the  old  diet  was  resumed,  and  after  nitrogen 
equilibrium  had  again  been  established,  the  same  propor- 
tion of  carbohydrate  was  omitted  from  the  diet,  but  alcohol 
was  not  substituted.  When  the  diet  was  poor  in  proteid 
it  was  found  that  less  proteid  was  lost  from  the  body  when 
the  alcohol  was  omitted  than  when  it  was  used,  indicating 
that,  so  far  from  protecting  the  tissues  of  the  body  by  its 
oxidation,  the  alcohol  exercised  a  directly  injurious  effect 
upon  proteid  consumption.  Numerous  other  researches 
might  be  quoted  to  show  that  the  effect  of  moderate  quan- 
tities of  alcohol  upon  body  metabolism  is  not  yet  satisfac- 
torily understood.  Before  making  any  positive  statements 
as  to  the  details  of  its  action,  it  is  wise,  therefore,  to  wait 
until  reliable  experimental  results  have  accumulated.  The 


214  I'JIYS/OLOGV. 

specific  action  of  alcohol  on  the  heart,  stomach,  and  other 
organs  has  been  investigated  more  or  less  completely,  but 
the  literature  is  too  great  and  the  results  are  too  uncertain 
to  permit  any  resume  to  be  given  here.  When  alcohol  is 
taken  in  excess  it  produces  the  familiar  symptoms  of  in- 
toxication, which  may  pass  subsequently  into  a  condition 
of  stupor  or  even  death,  provided  the  quantity  taken  is 
sufficiently  great.  So,  also,  the  long-continued  use  of 
alcohol  in  large  quantities  is  known  to  produce  serious 
lesions  of  the  stomach,  liver,  nerves,  blood  vessels,  and 
other  organs.  The  effect  of  alcohol  upon  the  body  evi- 
dently varies  greatly  with  the  quantity  used.  It  may 
perhaps  be  said  with  safety  that  in  small  quantities  it  is 
beneficial,  or  at  least  not  injurious,  barring  the  danger  of 
acquiring  an  alcohol  habit,  while  in  large  quantities  it  is 
directly  injurious  to  various  tissues." 

[From  THOMPSON'S  Practical  Dietetics.} 

"  .  .  .  the  following  general  propositions  comprise  the 
belief  of  many  authorities  who  have  devoted  careful  re- 
search to  this  exceedingly  important  topic  :  — 

"  i.  The  use  of  alcohol  in  any  shape  is  wholly  unneces- 
sary for  the  use  of  the  human  organism  in  health.  It  does 
not  exist  as  a  natural  product.  The  very  lowest  types  of 
man  —  Australian  and  many  Polynesian  savages  —  know 
nothing  of  it,  and  drink  only  water  and  fresh  fruit  juice, 
such  as  that  of  the  cocoanut,  although  they  speedily 
acquire  a  fondness  for  alcohol  when  it  is  given  them. 

"  2.  A  large  number  of  persons  are  undoubtedly  better 
without  alcohol,  and  may  prolong  their  lives  by  total  ab- 
stinence. 

"  3.  The  lifelong  use  of  alcohol  in  moderation,  as  an 
occasional  beverage  with  meals,  does  not  necessarily 


ALCOHOL.  215 

shorten  the  duration  of  life  or  induce  disease  in  some 
persons,  while  in  others  it  undoubtedly  produces  gradual 
and  permanent  changes,  chiefly  of  a  cirrhotic  character,  in 
the  blood  vessels  and  viscera,  such  as  the  liver  and  kidneys. 
These  alterations,  which  may  be  slow  and  subtile  in  char- 
acter, may  not  in  themselves  materially  impair  the  health 
or  cause  an  ultimately  fatal  result,  but  they  tend  to  weaken 
vital  organs  and  produce  a  condition  of  premature  senility  ; 
so  that  if  the  patient  be  overtaken  by  any  severe  disease, 
as,  for  example,  by  an  acute  infection  like  pneumonia,  or 
a  chronic  one  like  pulmonary  tuberculosis,  the  resistance 
of  the  body  to  the  force  of  the  disease  is  materially  im- 
paired, and  the  danger  to  the  patient  is  seriously  enhanced. 

"4.  There  are  many  persons  whose  constitutional  in- 
heritance is  such  that  they  should  be  particularly  warned 
against  the  use  of  alcohol,  and  in  some  such  cases,  as,  for 
example,  among  those  who  are  subjects  of  well-marked 
gouty  diathesis,  it  is  better  that  the  use  of  alcohol  should 
])e  imperatively  forbidden. 

"5.  The  abuse  of  alcoholic  stimulation  is  invariably 
injurious,  although  the  extent  to  which  evil  influences 
become  manifest  depends  upon  the  constitution  of  the 
individual,  in  connection  with  the  two  factors  of  heredity 
and  environment. 

"  6.  There  are  a  number  of  diseases  in  which  the  tem- 
porary use  of  alcohol  is  of  positive  service,  and  there  are  a 
number  of  cases  in  which  it  becomes  a  necessity  in  order 
to  prolong  life. 

"  7.  In  many  cases  of  malnutrition  and  malassimilation 
of  food,  alcohol  is  itself  a  food,  and  its  consumption  under 
proper  direction  results  in  an  increase  of  body  weight  and 
strength,  and  improvement  of  functional  activity.  These 
results  are  accomplished  in  part  through  the  action  of  the 


216 

alcohol  as  a  definite  food,  and  in  part  through  its  remark- 
able effect  in  force  production.  The  latter  is  due  to  its 
own  direct  combustion,  by  which  in  chronic  diseases  and 
in  critical,  acute,  and  exhausting  affections  it  spares  that 
of  the  tissues  of  the  body. 

"  Although  alcohol  is  such  a  strong  force  producer  and 
heat  generator,  its  effect  in  this  direction  is  very  soon 
counterbalanced  by  its  stronger  influence  in  lowering  the 
general  tone  of  the  nervous  system,  and  in  producing 
positive  degeneration  in  the  tissues.  In  the  condition  of 
health  more  food  is  usually  eaten  and  more  force  is  devel- 
oped than  is  actually  necessary  for  the  body,  and  there  is 
constantly  a  reserve  supply  of  energy  on  hand  which  may 
be  utilized  for  any  extraordinary  exertion,  and  hence  the 
constant  use  of  alcohol  as  a  food  or  stimulant  in  health  is 
both  unnecessary  and  unadvisable.  When  alcohol  is  con- 
sumed in  health  in  addition  to  a  normal  or  excessive  quan- 
tity of  solid  food,  by  its  more  ready  combustion  it  prevents 
the  complete  oxidation  of  the  latter,  and  favors  the  accy 
mulation  of  suboxidized  waste  products,  which  are  always 
harmful  in  the  system.  Excesses  in  eating  are  thus  doubly 
aggravated  by  the  effects  of  alcohol.  It  is  the  almost  uni- 
versal testimony  of  army  surgeons,  and  the  experience  of 
those  who,  like  Greely,  Stanley,  and  others,  have  led  long 
and  perilous  exploring  expeditions  involving  great  fatigue 
and  unusual  endurance,  that  muscular  overwork  and  cli- 
matic hardships  are  much  better  endured  if  alcohol  is 
entirely  abstained  from. 

"  It  has  always  been  found  in  armies  that  when  good 
food  was  at  hand  the  issue  of  alcohol  with  the  regular 
ration  produced  an  increased  percentage  of  sick  days  and 
of  incapacity  for  work.  Colonel  Alfred  A.  Woodhull, 
surgeon  United  States  army,  writes  me  in  regard  to  this 


ALCOHOL.  2i; 

matter  :  '  I  do  not  think  that  any  of  our  medical  officers 
would  seriously  advocate  the  issue  of  alcohol  as  a  measure 
of  health,  but  I  believe  that  its  habitual  use  during  the 
Rebellion  was  prohibited  for  reasons  of  discipline,  while  it 
still  might  have  been  occasionally  issued  as  if  for  health. 
On  the  rare  occasions  when  it  might  serve  a  good  purpose, 
as  a  temporary  stimulant  after  a  long  and  wet  march,  the 
wagons  would  be  in  the  rear,  owing  to  the  same  conditions 
that  fatigued  the  men.' 

"  While  all  this  applies  to  prolonged  effort  of  any  kind, 
and  to  conditions  where  other  food  can  be  obtained  and 
assimilated,  it  does  not  detract  from  the  fact  that  alcohol 
is  a  most  helpful  food  and  stimulant  in  emergencies,  when 
other  food  cannot  be  had,  or  when  the  body  is  temporarily 
endangered  from  acute  disease  and  the  higher  rate  of 
combustion  in  fever,  or  from  failure  to  assimilate  other 
nourishment. 

"  Captain  Woodruff,  assistant  surgeon  United  States 
army,  says :  '  Spirits  can  never  be  used  in  the  army  as  a 
regular  issue ;  the  practice  is  thoroughly  vicious,  and  was 
virtually  abandoned  sixty  years  ago.  On  extraordinary 
occasions  of  great  fatigue  they  are  allowable  in  modera- 
tion. Under  such  temporary  stimulation  the  men  will 
brace  up  and  perform  the  necessary  work  of  making  earth- 
works, etc.,  when  without  it  they  would  be  too  exhausted 
to  do  anything.  Without  such  stimulation  a  man  is  not 
worth  much  after  he  has  made  a  forced  march  of  forty 
miles.' 

"  The  problem  whether  the  world  as  a  whole  is  better  or 
worse  for  the  existence  of  alcohol,  aside  from  all  ethical 
questions,  and  viewed  merely  from  the  scientific  standpoint 
of  the  influence  of  alcohol  upon  mortality,  is  difficult  of 
solution ;  for  to  offset  the  numerous  cases  of  fatal  alcohol- 


218 

ism,  and  the  still  larger  number  of  cases  ol  diseases  which 
would  not  presumably  be  fatal  without  the  existing  condi- 
tion of  chronic  alcoholic  poisoning  of  the  system,  are  very 
many  cases  among  both  infants  and  adults  in  which  life  is 
undoubtedly  saved  by  the  prompt  resort  to  this  food  and 
stimulant,  and  its  energetic  use.  So  long  as  man  is  ex- 
posed to  hardships  and  conditions  arising  from  improper 
and  deficient  food  supply,  as  well  as  to  the  numerous  in- 
fectious diseases  to  which  he  is  heir,  alcohol  must  still  be 
regarded  rather  as  a  blessing  than  a  curse ;  for  there  is  no 
form  of  stimulant  and  food  combined,  or  stimulant  alone, 
which,  taken  all  in  all,  can  be  so  completely  relied  upon  in 
cases  of  emergency.  Alcohol,  when  taken  alone,  will  pro- 
long life  beyond  the  period  at  which  it  terminates  from 
starvation." 


BEVERAGES  CONTAINING  ALCOHOL. 

[RoHfe,  Text-Book  of  Hygiene.} 

"  The  physiological  action  of  alcohol  has  been  pretty 
fully  worked  out  by  Binz  and  his  pupils  and  by  other  ex- 
perimenters. From  these  researches  it  appears  that  the 
first  effect  of  taking  alcohol,  sufficiently  diluted,  into  the 
stomach  is  to  increase  the  flow  of  saliva  and  gastric  juice. 
This  effect  is  probably  reflex,  and  results  from  a  stimula- 
tion of  nerve  terminations  in  the  stomach.  The  alcohol  is 
rapidly  absorbed,  and  is  carried  in  the  blood,  without  un- 
dergoing chemical  change,  to  the  nervous  centers,  lungs, 
and  tissues  generally.  In  the  brain  the  alcohol  probably 
enters  into  combination  with  the  nervous  tissue,  modifying 
the  normal  activity  of  the  various  centers,  either  increasing 
the  activity,  if  the  alcohol  is  in  small  quantity  (stimulating 
effect),  or  diminishing  it,  if  in  larger  quantity  (depressing 


ALCOHOL.  219 

effect),  or  entirely  suspending  the  activity  of  the  centers 
if  in  sufficiently  large  quantity  (paralyzing  effect). 

"  Alcohol  stimulates  the  vasodilator  nerves,  causing  dila- 
tation of  the  smaller  vessels ;  in  consequence  of  this  the 
blood  is  largely  sent  to  the  periphery  of  the  body,  the 
blood  pressure  diminishes,  and  heat  radiation  is  increased. 
At  the  same  time  a  portion  of  the  alcohol  is  used  up  in  the 
production  of  animal  heat,  thus  economizing  the  expendi- 
ture of  fats  and  proteids,  and  acting  as  a  true  respiratory 
food.  Alcohol  does  not  contribute  nutritive  material  to 
the  body ;  it  only  permits  that  which  is  stored  up  to  be 
saved  for  other  uses,  by  furnishing  easily  oxidizable  (com- 
bustible) material  for  carrying  on  the  respiratory  process 
and  supplying  animal  heat. 

"  During  the  use  of  alcohol  the  excretion  of  urea  is 
diminished.  This  shows  that  waste  of  tissue  is  retarded 
in  the  body. 

"  Regarding  the  statement  of  some  authorities  that  alco- 
hol does  not  undergo  any  change  in  the  body,  but  is  ex- 
creted unchanged,  Binz  asserts  that  alcohol  appears  in  the 
urine  only  when  exceptionally  large  quantities  have  been 
taken,  and  then  in  very  small  proportion.  It  is  not  excreted 
by  the  lungs,  the  peculiar  odor  of  the  breath  being  due  not 
to  the  alcohol,  but  to  the  volatile  aromatic  ether,  which  is 
oxidized  with  greater  difficulty,  and  so  escapes  unchanged. 

"  While  alcohol  produces  subjectively  an  agreeable  sen- 
sation of  warmth  in  the  stomach  and  on  the  surface  of  the 
body,  the  bodily  temperature  is  not  raised.  The  subjective 
sensation  is  due  to  the  dilatation  of  the  blood  vessels  and 
the  sudden  hyperaemia  of  those  parts. 

"  During  fevers  and  other  exhausting  diseases  alcohol  is  in- 
valuable to  prevent  waste  of  tissue  and  sustain  the  strength. 
It  does  not  act  merely  as  a  stimulant  to  the  circulation  and 


220  PHYSIOLOGY. 

nervous  system,  but,  as  above  pointed  out,  saves  the  more 
stable  compounds  by  furnishing  a  readily  oxidizable  res- 
piratory food. 

"  When  taken  in  small  doses  by  healthy  persons  alcohol 
diminishes  the  temperature  by  increasing  heat  radiation. 
When  large  quantities  are  taken  the  bodily  temperature  is 
reduced  by  diminishing  heat  production,  as  well  as  by  in- 
creased radiation.  This  is  shown  in  the  condition  known 
as  dead-drunkenness,  in  which  the  temperature  is  some- 
times depressed  as  much  as  20  degrees  F.  below  the 
normal.  Cases  in  which  the  temperature  sank  to  75  de- 
grees, 78.8  degrees,  and  83  degrees  F.  have  been  reported, 
with  recovery  in  all  cases. 

"The  constant  use  of  alcohol  produces  in  all  the  organs 
an  excess  of  connective  tissue,  followed  by  fatty  degenera- 
tion and  the  condition  known  as  cirrhosis.  The  organs 
most  frequently  affected  are  the  stomach,  liver,  and  kid- 
neys. Serious  pathological  alterations  also  occur  in  the 
circulatory,  respiratory,  and  nervous  systems. 

"Alcohol  is  not  necessary  to  persons  in  good  health. 
Probably  most  persons,  regardless  of  their  state  of  health, 
do  better  without  it.  Its  habitual  use,  in  the  form  of 
strong  liquors,  is  to  be  unreservedly  condemned.  The 
lighter  wines  and  malt  liquors,  if  obtained  pure,  may  be 
consumed  in  moderate  quantities  without  ill  effects.  Even 
in  these  forms,  however,  the  use  of  alcohol  should  be  dis- 
couraged, or  perhaps  prohibited,  in  the  young. 

"  Neither  in  hot  nor  in  cold  climates  is  alcohol  necessary 
to  the  preservation  of  health,  and  its  moderate  use  even 
produces  more  injury  than  benefit.  The  polar  voyager 
and  the  East  Indian  merchant  are  alike  better  off  without 
alcohol  than  with  it. 

"  It  has  long  been  a  prevalent  belief  that  the  use  of 


ALCOHOL.  221 

alcohol  enables  persons  to  withstand  fatigue  better  than 
where  no  alcohol  is  used.  A  large  amount  of  concurrent 
testimony  absolutely  negatives  this  belief. 

"The  predisposition  to  many  diseases  is  greatly  in- 
creased by  the  habitual  use  of  alcohol.  Sunstroke,  the 
acute  infectious  diseases,  and  many  local  organic  affec- 
tions, attack,  by  preference,  the  intemperate.  A  recent 
collective  investigation  by  the  British  Medical  Association 
brought  out  the  fact  that  croupous  pneumonia  is  vastly 
more  fatal  among  the  intemperate  than  among  those- who 
abstained  from  the  use  of  alcoholic  liquors." 

Testimony  of  a  Naturalist.  —  W.  T.  Hornaday,  author 
of  Two  Years  in  the  Jungle,  who  has  had  years  of  ex- 
perience as  collector  in  many  lands,  has  the  following  to 
say  as  to  the  use  of  alcoholic  drink  :  "  While  a  traveler  or 
hunter  should  never  drink  brandy  or  whisky  as  a  bever- 
age, it  is  a  most  excellent  thing  to  have  in  many  cases  of 
sickness  or  accident,  when  a  powerful  stimulant  is  neces- 
sary. Above  all  things,  however,  which  go  farthest  toward 
preserving  the  life  of  the  traveler  against  diseases  and 
death  by  accident,  and  which  every  naturalist  especially 
should  take  with  him  wherever  he  goes,  are  Jiabits  of  strict 
temperance.  In  the  tropics  nothing  is  so  deadly  as  the 
drinking  habit,  for  it  speedily  paves  the  way  to  various 
kinds  of  disease  which  are  always  charged  to  the  account 
of  'the  accursed  climate.'  If  a  temperate  man  falls  ill 
or  meets  with  an  accident,  his  system  responds  so  readily 
to  remedies  and  moderate  stimulants  that  his  chances  of 
recovery  are  a  hundred  per  cent  better  than  those  of  the 
man  whose  constitution  has  been  undermined  by  strong 
drink.  There  are  plenty  of  men  who  will  say  that  in  the 
tropics  a  little  liquor  is  necessary,  'a  good  thing,'  etc.;  but 


222  PHYSIOLOGY. 

let  me  tell  you  it  is  no  such  thing,  and  if  necessary  I  could 
pile  up  a  mountain  of  evidence  to  prove  it.  The  records 
show  most  conclusively  that  it  is  the  men  who  totally 
abstain  from  the  use  of  spirits  as  a  beverage  who  last 
longest,  have  the  least  sickness,  and  do  the  most  and  best 
work.  As  a  general  rule,  an  energetic  brandy  drinker  in 
the  ju-ngle  is  not  worth  his  salt,  and  as  a  companion  in  a 
serious  undertaking,  is  not  even  to  be  regarded  as  a  pos- 
sible candidate."  These  statements  are  made,  with  no 
thought  of  sermonizing,  simply  as  practical  advice  to 
collectors. 

[HALLIBURTON,  Text-Book  of  Chemical  Physiology  and  Pathology.} 

"  Alcohol.  —  Small  quantities  of  the  alcohol  taken  leave 
the  body  by  the  breath  and  urine  as  such,  the  greater 
amount  is  decomposed  into  simpler  products  (acetic,  oxalic, 
carbonic  acids,  and  water);  the  formation  of  these  must 
give  rise  to  a  certain  amount  of  bodily  heat.  It  has  been 
calculated  that  a  man  can  burn  off  in  his  body  two  ounces 
of  absolute  alcohol  daily.  Alcohol  is  thus,  within  narrow 
limits,  a  food.  It,  however,  lessens  proteid  metabolism  by 
about  six  per  cent,  and  thus  ultimately  leads  to  a  diminution 
of  the  heat  produced  in  the  body.  It  is,  moreover,  a  very 
uneconomical  food ;  much  more  nutriment  would  have 
been  obtainable  from  the  barley  or  the  grapes  from  which 
it  was  made.  The  value  of  alcohol  used  within  moderate 
limits  is  not  as  a  food,  but  as  a  stimulant  not  only  to 
digestion,  but  to  the  heart  and  brain." 

[M'KKNDRICK,  Text-Book  of  Physiology.} 

"With  regard  to  alcohol,  its  exact  influence,  when  taken 
in  moderation  by  those  who  use  it  as  an  article  of  diet, 
cannot  be  precisely  stated.  It  has  been  asserted  by 
several  observers  that  alcohol  is  eliminated  from  the  body 


ALCOHOL.  223 

as  alcohol  by  the  various  excretory  channels.  The  evi- 
dence of  this  is  doubtful,  and  it  is  probable  that  it  is  split 
up  into  simpler  compounds.  ...  A  small  part  of  the 
alcohol  ingested  no  doubt  is  exhaled  by  the  mucous  mem- 
brane of  the  lungs  and  by  the  kidneys.  The  odor  of  the 
breath  depends  on  the  elimination  of  oxidation  products, 
such  as  fusel  oil.  If  oxidized  even  to  a  small  extent,  and 
the  evidence,  as  already  indicated,  points  to  the  oxidation 
of  by  far  the  larger  proportion  of  it  (95  per  cent),  alcohol 
must  be  regarded,  in  the  scientific  sense,  as  a  food.  No 
doubt  also  its  ingestion  diminishes  the  metabolism  of  pro- 
teids  to  the  extent  of  about  6  per  cent,  as  shown  by  the 
diminished  excretion  of  urea.  Its  oxidation  will  also  be 
attended  by  the  production  of  heat  ;  but  as,  on  the  other 
hand,  it  lessens  the  production  of  heat  by  interfering  with 
the  metabolism  in  proteid  tissues,  and  also  by  diminishing 
the  oxidation  of  carbohydrates  and  fats,  the  final  result 
is  an  actual  diminution  of  bodily  temperature.  While, 
therefore,  alcohol  must  be  classed  technically  as  a  food, 
it  is  in  many  respects  an  unsuitable  food,  and  its  place  can 
be  taken  with  great  advantage  by  other  substances.  In 
small  doses  it  acts  as  a  local  excitant  of  the  digestive 
mucous  membrane,  and  afterwards  as  a  diffusible  stimu- 
lant upon  the  circulation  and  central  nervous  system.  In 
some  cases  it  may  aid  the  digestive  process,  but  in  a  state 
of  health  it  is  not  only  not  required,  but  its  use,  except  in 
small  doses,  is  positively  prejudicial." 

Physiological  Effects  of  Alcohol.  —  These  various  au- 
thorities have  thus  been  freely  quoted,  to  show  that  while 
there  is  considerable  divergence  of  opinion  in  regard  to 
some  of  the  physiological  effects  of  alcohol,  they  are  sub- 
stantially agreed  as  to  the  following  points:  — 


224  PHYSIOLOGY. 

1.  Alcohol  is  not  needed  in  health. 

2.  While  technically  it  may  be  called  a  food,  practically 
it  is  a  poison,  and  its  use  is  dangerous. 

The  danger  is  especially  great  where  there  is  a  latent 
hereditary  tendency  to  inebriety  or  insanity.  The  danger 
is  also  very  great  when  the  disease  for  which  alcohol  is 
prescribed  is  accompanied  by  melancholy  and  depression. 
Many  individuals,  on  finding  a  drug  which  exhilarates  and 
banishes  the  weight  of  oppression  by  which  they  are  borne 
down  are  tempted  beyond  their  power  of  resistance,  even 
though  the  reaction  brings  them  into  a  worse  condition 
than  the  one  from  which  they  sought  relief. 

The  Danger  of  using  Alcohol.  —  The  pressure  of  modern 
life,  and  the  intensity  of  the  struggle  for  a  living,  brings 
about  a  condition  of  nervous  strain  that  is  fraught  with 
great  danger.  Every  thinking  man  should  see  that  to  use 
alcoholic  drink  for  the  relief  of  such  a  condition  is  like 
venturing  out  in  a  boat  above  the  Falls  of  Niagara,  —  he 
knows  not  when  the  rushing,  mighty  power  will  gain  the 
mastery  and  dash  him  to  destruction. 

READING.  —  The  Temperance  Teachings  of  Science,  Pal- 
mer; The  Foundation  of  Death,  a  Study  of  the  Drink 
Question,  Gustafson. 


Summary.  —  i.   Alcohol  is  a  very  dangerous  drug  and  should  be 
used  only  when  prescribed  by  a  physician. 

2.  Athletes  avoid  alcohol  when  training. 

3.  A  large  per  cent  of  crime  is  due  to  alcohol. 

4.  On  account  of  its  rapid  absorption  alcohol  is  a  quick  recupera- 
tive after  collapse. 

5.  In   small   amounts  alcohol  is  oxidized  in  the  body,  producing 
energy. 


ALCOHOL.  225 

6.  Alcohol  usually  lowers  the  temperature  of  the  body  through  the 
increased  skin  circulation. 

7.  It  is  especially  dangerous  to  take  alcoholic  drink  when  exposed 
to  severe  cold,  as  in  arctic  explorations. 

8.  In  the  army  alcoholic  drink  as  a  regular  ration  did  more  harm 
than  good  ;  hence  was  discontinued. 

9.  More  hard  work  can  be  endured  without  alcohol  than  with  it. 
10.    The  precise  effects  of  alcohol  are  hard  to  determine.    But  every- 
body knows  that  its  effects  are  generally  bad. 

Questions.  —  i .    Why  do  some  persons  think  that  alcoholic  drink 
makes  them  warmer  ? 

2.    What   do   statistics   show  as  to  "expectation  of  life"  among 
abstainers  and  alcohol  users  ? 


CHAPTER   XIV. 
EXERCISE  AND   BATHING 

How  Exercise  is  Beneficial.  -The  full  significance  of 
the  benefits  of  muscular  exercise  could  not  be  understood 
when  we  studied  the  muscles,  and  before  we  had  studied 
the  blood  and  its  work  in  the  tissues  of  the  body  generally. 
Now  we  can  comprehend  how  exercise  stimulates  the  cells 
to  activity,  renews  the  lymph  around  the  cells  both  by 
quickening  the  blood  flow  and  by  pressure  on  the  lymph 
tubes ;  how  the  glands  of  excretion  are  set  to  work  more 
actively,  and  the  more  rapid  blood  stream  brings  away  the 
material  to  be  thrown  out. 

Exercise  for  General  Health.  —  Exercise  is  not  merely 
for  the  muscles.  It  quickens  the  action  of  the  whole  body 
by  increasing  cell  activity.  It  helps  clean  out  the  system 
and  clear  the  brain  as  well.  We  read  Blaikie's  admira- 
ble book,  How  to  Get  Strong,  and  learn  not  merely  to 
strengthen  the  muscles,  but  how  to  get  strong  to  do  the 
work  we  have  to  do  daily,  how  to  feel  well  every  day,  how 
not  only  to  do  our  work,  but  to  do  it  gladly,  and  with  a 
little  extra  good  cheer  that  may  radiate  from  us  and  in- 
spire others.  We  have  no  right  and  no  need  to  carry  the 
sour  visage  of  a  devitalized  body.  Good  health  is  attain- 
able, and  ought  to  be  attained,  by  nearly  all.  Attention 
must  be  paid  to  the  laws  of  our  being.  It  takes  some 
effort,  mental  as  well  as  physical,  to  adopt  and  observe 

226 


EXERCISE  AND  BATHING.  22J 

regular  hours  for  exercise  and  relaxation  and  to  be  careful 
in  diet. 

Nature's  Rewards  and  Punishments.  —  But  nature 
rewards  for  obedience  by  the  delight  of  a  healthy  body ; 
and  she  never  forgets  and  never  forgives,  nor  fails  to  pun- 
ish every  violation  of  every  one  of  her  laws.  Nature  makes 
no  threats  beforehand.  She  does  not  even  tell  us  her 
rules.  But  we  may  find  what  they  are  by  careful  obser- 
vation. 

Exercise  prolongs  Life.  —  Many  men  would  live  longer, 
feel  vastly  better,  and  do  greater  good  in  the  world  if  they 
would  take  regular  and  systematic  exercise  or  recreation 
(and  this  should  be,  literally,  re-creation).  It  is  a  short- 
sighted policy  to  say,  "  I  cannot  afford  the  time."  Not  to 
take  time  for  exercise  is  to  mortgage  one's  future.  Lord 
Derby  says,  "  He  who  does  not  take  time  for  exercise  will 
have  to  take  time  for  illness."  The  latter  half  of  every 
person's  life  ought  in  many  respects  to  be  by  far  the  most 
productive  of  good.  But  many  cut  off  this  half,  or  render 
it  less  productive  through  breaking  down  in  health  as  a 
consequence  of  violating  the  laws  of  hygiene.  Thus  one 
defeats  his  own  ends  in  life,  and  robs  the  world  of  the  debt 
he  owes  it,  that  of  returning  to  it,  in  his  riper  years,  some- 
thing for  the  help  it  gave  to  him  in  his  early  years  while 
he  had  not  yet  reached  the  fullest  mental  maturity.  It  is 
sad  enough  that  so  magnificent  a  structure  as  the  human 
body  must  perish  and  become  part  of  the  common  clay. 
But  it  is  infinitely  more  sad  to  think  that  it  has  not  fulfilled 
its  purpose  when  the  end  comes  in  what  should  be  mid- 
career.  Each  of  us  should  leave  the  world  better  than  he 
found  it,  and  our  ability  and  opportunities  for  doing  this 
increase  as  we  reach  middle  life. 


228  PHYSIOLOGY. 

Forms  of  Exercise.  —  In  selecting  the  kind  of  exercise 
the  old  lines  fit  well :  — 

"  In  whate'er  you  sweat,  indulge  your  taste ; 
The  toil  you  hate  fatigues  you  soon, 
And  scarce  improves  your  limbs.'1 

Of  course  this  does  not  mean  that  a  boy  should  refuse 
to  saw  wood  because  he  dislikes  it,  and  spend  all  his  time 
playing  ball.  But  for  older  persons,  especially  those  of 
sedentary  occupation,  exercise  that  exhilarates  is  far  more 
beneficial  than  that  which  is  not  enjoyed.  One  may  take 
a  walk  and  carry  all  his  cares  and  anxieties  with  him,  but 
he  is  not  likely  to  think  of  such  matters  when  playing 
tennis  with  a  good  opponent.  Whether  it  be  horseback 
riding,  cycling,  boxing,  boating,  skating,  or  other  form  of 
exercise,  choose,  whenever  a  choice  is  possible,  that  which 
you  thoroughly  enjoy.  Exercise  should  be  taken  out 
doors  whenever  possible.  The  gymnasium  is  a  substitute 
in  bad  weather. 

Games  of  School  Children.  —  Most  of  the  games  of 
school  children  are  excellent  kinds  of  exercise.  Cases 
have  been  reported  of  injury  from  excessive  skipping  the 
rope.  But  in  moderate  degree  it  is  a  good  exercise.  Tag, 
snowballing,  racing,  the  various  games  of  ball,  jumping, 
hopping,  and  other  games  may  be  played  on  the  school 
grounds. 

Tennis. — Tennis  is  a  fine  game,  and  suitable  for  girls 
as  well  as  boys.  It  has  the  great  advantage  over  baseball 
that  it  does  not  require  a  large  ground  (which  often  means 
going  some  distance  from  the  school  grounds  or  from 
home).  Two  can  make  up  a  game,  and  a  little  time  can 
be  better  utilized  than  with  the  games  requiring  more 
players.  The  exercise,  too,  is  more  evenly  distributed. 


EXERCISE  AND  BATHING  2 29 

There  is  no  long  waiting,  as  in  some  games,  but  a  constant 
interchange  of  play,  active  but  not  severe,  with  practically 
no  danger  of  injury. 

Baseball  and  Football.  —  For  those  who  can  pursue 
the  more  vigorous  games  of  baseball  and  football  they  are 
admirable,  and  should  not  be  objected  to  because  occa- 
sional injury  comes  from  them.  No  vigorous  exercise  is 
wholly  unattended  by  risk,  though  it  is  usually  slight  when 
the  proper  care  is  used.  All  these  games  calling  for  great 
activity  and  strength  develop  manly  qualities  in  boys,  and 
do  much  to  make  them  active,  fearless  men,  men  who  in 
time  of  danger  have  not  only  strength  and  endurance,  but 
well-trained  muscles,  cool  heads,  and  brave  hearts,  men 
who  know  what  to  do  and  how  to  do  it  in  an  accident,  as 
at  fires,  upsetting  of  boats,  etc.  A  few  strong,  cool-headed 
men,  by  their  presence  of  mind,  often  stop  a  panic  and 
save  many  lives  when  there  is  an  alarm  of  fire,  which  often 
proves  false.  The  Duke  of  Wellington  said  that  it  was 
on  the  football  fields  of  Eton  and  Rugby  that  the  battle 
of  Waterloo  was  won. 

Boxing.  —  Boxing  is  a  splendid  exercise.  It  calls  into 
play  nearly  every  muscle  of  the  body.  Many  pieces  of 
apparatus  in  a  gymnasium  are  for  the  especial  purpose 
of  working  certain  muscles.  But  a  pair  of  boxing  gloves 
may  be  said  to  contain  a  whole  gymnasium.  Many  kinds 
of  work  in  a  gymnasium  are  likely  to  be  overdone,  espe- 
cially if  not  under  the  direct  supervision  of  a  good  director. 
One  may  overlift  or  overstrain  himself.  But  in  boxing 
there  is  little  tendency  in  this  direction.  Boxing  makes 
one  quick  on  his  feet,  trains  to  quick  movements  of  the 
arms,  trains  the  eye,  keeps  the  body  in  an  erect  position, 
and  especially  develops  the  muscles  of  the  legs  and  back. 


230 


bi  ings  out  the  chest  and  shoulders.  It  develops 
the  "wind,"  and  keeps  one  in  constant  action.  It  teaches 
control  of  the  temper  more  than  almost  any  form  of  exer- 
cise. It  develops  a  degree  of  self-reliance  that  is  worth 
much.  Instead  of  developing  a  tendency  to  become  in- 
volved in  quarrels,  it  prevents  getting  into  such  disgraceful 
affairs.  The  man  who  knows  that  he  can  defend  himself 
when  it  becomes  necessary  is  far  less  likely  to  pay  serious 
attention  to  idle  bluster  and  slight  provocation  than  one 
not  so  trained.  And  it  may  prove  valuable  to  know  how 
to  defend  one's  self  from  the  attack  of  a  ruffian,  or  bully, 
or  drunken  brute,  or  other  infuriated  animal.  The  cool- 
ness of  head,  the  quick  judgment,  and  prompt  action  of 
a  trained  boxer  frequently  saves  one  from  serious  injury, 
and  adds  not  a  little  to  personal  comfort.  Like  tennis, 
boxing  calls  for  little  apparatus,  little  space,  and  only  two 
persons.  In  many  places  where  ordinary  gymnasium 
work  is  out  of  the  question,  boxing  is  available.  It  is 
indeed  a  "manly  art,"  and  the  doctrine  taught  in  Tom 
Brown  s  School  Days  at  Rugby  is  as  wholesome  as  can  be 
given  to  boys  to  make  them  strong  and  active,  to  give 
them  physical  and  moral  health. 

Bicycling.  —  This  is  an  excellent  exercise,  as  it  is  in 
the  open  air  and  exhilarating.  There  is  danger  of  over- 
exertion,  and  it  is  bad  for  one  to  yield  to  the  temptation 
to  make  long  runs.  There  is  danger  of  overtaxing  the 
heart.  The  handle  bar  should  be  adjusted  to  allow  a 
fairly  upright  position.  The  saddle  should  be  such  as  not 
to  sustain  the  weight  on  the  perineum. 

Exercise  for  Middle-aged  Men.  —  For  men  in  middle  life,  in  most 
cases,  milder  exercises  are  preferable,  such  as  shooting,  fishing,  and 
horseback  riding.  Every  person  should  have  some  form  of  exercise 
that  takes  him  into  the  open  air  daily.  The  English  are  more  given 


EXERC/SE  AND   BATHING.  231 

to  their  "  constitutionals "*  than  their  American  cousins,  and  are  the 
better  for  it.  Doubtless  if  we  paid  more  attention  to  these  matters, 
we  should  lose  something  of  our  national  reputation  as  a  '"nervous 
people.11  English  women  are  noted  walkers,  and  do  not  seem  to  pride 
themselves  on  the  smallness  of  their  feet.  The  signs  of  the  times 
would  appear  to  show  that  we  are  improving  in  this  respect.  Probably 
Americans  make  too  much  use  of  street  cars.  Walking  is  the  cheapest 
exercise,  and  every  one  can  afford  to  take  it.  For  those  who  can 
afford  it  horseback  riding  is  admirable.  As  Dr.  Holmes  expressed  it, 
"saddle  leather  is  in  some  respects  even  preferable  to  sole  leather; 
the  principal  objection  to  it  is  of  a  financial  character.''  Lord  Palmer- 
ston  said  "the  outside  of  a  horse  is  the  best  thing  for  the  inside  of 
a  man.11  Perhaps  livery  bills  would  prove  cheaper  and  more  agreeable 
than  doctors1  bills. 

" Taking  Cold."  —  So  long  as  one  is  actively  exercising, 
he  is  not  likely  to  take  cold.  But  if  one  rests  in  a  cool 
place,  especially  when  he  is  warm,  he  is,  as  we  all  too  well 
know,  likely  to  take  cold.  As  we  saw  when  we  were 
studying  the  circulation  of  the  blood,  the  application  of 
cold  to  the  skin  causes  the  arteries  (through  reflex  action) 
to  become  smaller.  Thus  when  resting  in  a  cool  place  the 
skin  becomes  pale  and  cold. 

During  a  "  cold  "  there  is  fever.  The  regulation  of  the 
heat  by  the  skin  is  interfered  with.  At  the  same  time  it 
is  often  noticeable  that  the  urine  is  more  abundant  than 
usual.  As  cold  may  lead  to  fatal  lung  disease,  so  it  may 
be  the  beginning  of  some  disease  of  the  kidneys  that  may, 
in  the  end,  bring  fatal  results. 

Diarrhea.  —  Diarrhea,  which  is  a  catarrhal  condition  of  the  intes- 
tine, may  follow,  or  be  associated  with,  a  cold,  and  as  a  result  of  this 
the  process  of  absorption  is  often  largely  checked.  There  is  a  great 
increase  in  the  secretion  of  mucus  by  the  mucous  glands  in  the  intes- 
tinal wall.  As  the  various  liquids  of  digestion  are  all  taken  from  the 
blood,  it  is  evident  that  if  some  returns  are  not  soon  made,  the  system 
must  become  bankrupt.  It  is,  then,  more  easy  to  understand  the  ex- 


232  PHYSIOLOGY. 

cessive  weakness  and  feeling  of  utter  prostration  that  we  experience 
during  an  acute  attack  of  diarrhea.  We  can  now  understand  where  all 
the  material  comes  from  to  make  the  profuse  discharges,  especially 
after  we  have  ceased  eating  for  some  time. 

It  is  a  significant  fact  that  diarrhea  is  usually  called  "  summer  com- 
plaint." During  the  warm  summer  nights  we  are  tempted  to  go  to 
sleep  with  very  little  covering  over  our  bodies.  But  it  almost  always 
grows  cool  before  morning.  The  common  summer  diarrhea  is,  in 
many  cases,  due  to  bacteria  taken  in  food ;  but,  on  the  other  hand,  may 
be  simply  a  "cold  in  the  bowels." 

Bathing.  —  One  purpose  of  bathing  is  to  cleanse  the 
skin.  For  this  purpose  warm  water  is  best,  and  it  is  de- 
sirable to  use  soap,  especially  on  those  parts  which  are 
especially  exposed  to  contamination,  such  as  the  hands, 
the  feet,  the  armpits,  and  groins. 

Cold  Baths.  —  Another  important  function  of  bathing 
is  to  act  as  a  systemic  tonic.  For  this  purpose  cold  bath- 
ing is  better,  but  this  should  not  be  too  long  continued, 
and  must  be  followed  by  brisk  friction  to  give  the  skin  a 
ruddy  glow.  For  this  kind  of  bath  a  tub  is  not  necessary, 
and  hardly  desirable.  The  water  may  be  quickly  applied 
by  means  of  a  sponge,  and  the  body  thoroughly  rubbed 
with  a  coarse  towel.  The  whole  process  should  be  com- 
pleted very  quickly,  especially  if  the  room  be  not  warm. 

Bath  Hits.  —  Instead  of  the  sponge  and  the  ordinary 
form  of  towel,  it  may  be  found  more  convenient  to  use 
bath  mits  made  of  Turkish  toweling.  These  are  easily 
made,  and  are  somewhat  more  convenient,  as  thus  friction 
may  be  more  readily  applied  than  with  a  towel,  which  is 
apt  to  slip  in  the  hand.  The  two  hands  may  be  used  at 
the  same  time,  and  the  whole  time  of  the  bath  need  not 
exceed  two  or  three  minutes.  At  the  beginning  of  a  bath, 
cold  water  should  be  applied  to  the  head  and  face. 


EXERCISE  AND  BATHING.  233 

Time  for  Bathing.  —  For  students,  or  others  who  do 
not  take  a  great  deal  of  vigorous  exercise,  which  keeps 
the  skin  active,  this  means  of  keeping  the  skin  active  is 
especially  valuable.  The  use  of  warm  water  for  cleansing 
seems  best  adapted  (for  busy  people)  to  the  time  of  going 
to  bed.  But  the  best  time  for  the  cool  bath  is  on  getting 
up  in  the  morning. 

Warm  Baths  vs.  Cold  Baths.  —  Prolonged  warm  baths 
are  debilitating,  and  probably  increase  a  tendency  to  take 
cold,  whereas  cold  bathing  is  one  of  the  very  best  means 
of  fortifying  against  cold,  and  especially  against  the  ten- 
dency to  take  cold  on  slight  exposure.  For  most  'persons 
a  cool  sponge  bath,  on  rising,  will  act  as  a  most  excellent 
tonic ;  but  if  it  seems  to  produce  neuralgia,  it  should  be 
used  with  caution. 

Exercise  of  Arterial  Muscles.  —  We  have  learned  that 
the  blood  supply  to  any  organ  is  regulated  by  the  action 
of  the  plain  muscle  fibers  in  the  walls  of  the  small  arter- 
ies. Now,  when  we  are  subject  to  changes  in  temperature 
these  muscles  get  exercise,  and  one  writer  has  well  called 
the  cold  bath  the  gymnastics  of  the  plain  muscle  fibers, 
and  we  can  understand  how  the  system  can  be  trained  to 
adjust  itself  to  cold,  and  enabled  to  avoid  " taking  cold" 
so  frequently. 

Habit  of  Cold  Bathing  acquired  Gradually.  —  There 
are  undoubtedly  many  persons  who  do  not  profit  by  cold 
bathing,  but  probably  many  of  these  would  soon  adapt 
themselves  to  it  by  beginning  with  tepid  water  and  gradu- 
ally using  cooler.  To  stand  stripped  in  a  cold  room,  of 
course,  is  not  a  safe  thing  to  do.  And  the  great  secret  of 
the  benefit  that  may  be  expected  from  the  operation,  as 
most  people  are  situated,  is  to  be  very  brisk,  the  whole 


234 

process  occupying  only  a  few  minutes.  Many  are  opposed 
to  cold  sponge  bathing,  and  condemn  it  without  reserve, 
when,  probably,  they  have  never  really  given  it  a  fair  trial. 
Let  it  be  repeated,  with  emphasis,  that  for  students  it  is 
one  of  the  very  best  means  of  preserving  health. 

READING.  —  Baths   and  Bathing  (Health    Primers,    D. 
Appleton  &  Co.). 


Summary.  —  i.    Exercise  stimulates  the  activity  of  all  the  organs, 
by  promoting  cell  activity  and  assisting  excretion. 

2.  Exercise  should  be  in  the  open  air  as  much  as  possible. 

3.  Exercise  is  more  beneficial  when  it  exhilarates. 

4.  Exercise  should  be  taken  regularly. 

5.  Warm  baths  are  best  for  cleansing,  and  a  good  time  is  at  bed- 
time. 

6  Cold  baths  stimulate  the  circulation  of  blood  in  the  skin,  and 
serve  as  a  tonic  to  the  whole  system.  Just  after  rising  is  a  good  time 
for  the  cold  bath. 

7.    The  cold  bath  fortifies  against  taking  cold. 

Questions. —  I.    Should  exercise  be  carried  to  the  point  of  fatigue  ? 

2.  How  can  one  avoid  taking  cold  after  exercise  ? 

3.  Do  girls  need  exercise  as  much  as  boys  ? 

4.  What  is  the  condition  of  the  body  during  a  "  cold  "  ? 

5.  How  may  a  cold  be  caused  ? 

6.  How  may  a  cold  be  cured  ? 

7.  How  may  a  cold  be  prevented  ? 

8.  Why  do  some  persons   take  cold  so  much  more  readily  than 
others  ? 

9.  Why  does  the  same  person  take  cold  more  readily  at  one  time 
than  at  another  ? 

10.  How  often  should  a  person  bathe  ? 

1 1 .  What  hour  is  best  for  sea  bathing  ?     Why  ? 


CHAPTER   XV. 
THE   BRAIN. 

THE  muscles  are  the  executive  organs ;  but  the  seat 
of  the  will  is  the  brain. 

If  models  of  the  brain  can  be  obtained,  they  should 
be  carefully  studied.  If  not,  the  accompanying  figures 
may  be  used  in  their  stead. 

The  Coverings  of  the  Brain.  —  There  are  two  readily 
distinguishable  coats  of  the  brain,  the  dura  mater,  a  tough 
membrane,  adhering  more  or  less  closely  to  the  inside 
of  the  skull ;  and  the  pia  mater,  next  to  the  brain,  a  much 
thinner  membrane,  traversed  by  blood  tubes,  and  dipping 
down  into  the  grooves  between  the  convolutions  of  the 
cerebrum. 

The  Parts  of  the  Brain.  —  The  larger  and  upper  part 
of  the  brain  is  the  cerebrum  ;  below  and  back  of  this  is 
the  smaller  cerebellum ;  the  part  of  the  spinal  cord  within 
the  cranium  is  generally  reckoned  as  part  of  the  brain. 

The  Cerebrum.  —  The  cerebrum  consists  of  two  lateral 
hemispheres,  separated  by  a  deep  median  groove.  The 
surface  of  the  cerebrum  is  in  irregular  ridges,  the  con- 
volutions. The  outside  of  the  brain  consists  of  gray 
matter,  whereas  the  outside  of  the  spinal  cord  is  white. 
The  inner  part  of  the  brain  is  white,  and  the  two  halves 
are  connected  by  a  broad  band  of  white  matter,  which 
consists  of  many  white  fibers. 

235 


236  PHYSIOLOGY. 

The  Cerebellum.  —  The  cerebellum  is  much  smaller 
than  the  cerebrum,  and  has  fine  transverse  ridges  and 
grooves  in  place  of  the  convolutions  of  the  cerebrum.  It 
is  also  of  a  deeper  color,  a  reddish  gray.  The  cerebrum 
overlaps  the  cerebellum  so  that  the  latter  could  not  be 
seen  from  above  if  the  whole  brain  were  laid  bare.  But 
in  the  lower  animals  the  parts  of  the  brain  are  more  in 
a  series,  one  behind  the  other,  and  in  a  line  with  the 
spinal  cord. 

The  Spinal  Bulb.  —  The  enlarged  beginning  of  the 
spinal  cord,  often  called  the  medulla  oblongata,  is  the 
spinal  bulb.  It  is  white  like  the  rest  of  the  cord. 

The  Brain  of  a  Cat  or  Rabbit.  —  The  brain  of  a  cat  or  rabbit  may 
be  exposed  by  first  mounting  the  specimen  as  directed  for  showing  the 
spinal  cord  (see  p.  27).  After  removing  the  skin  from  the  upper  part 
of  the  head,  the  bone  should  be  cut  away  between  the  eyes  with  a  pair  of 
bone  forceps.  Cautiously  working  backward,  the  whole  of  the  brain 
may  be  unroofed.  Great  care  must  be  exercised,  for  here  we  have  one 
of  the  softest  tissues  of  the  body  lying  very  closely  beneath  one  of  the 
hardest.  It  is  possible  to  do  this  with  a  strong  knife,  but  the  bone 
forceps  save  a  great  deal  of  hard  work.  The  bone  must  be  broken 
away  bit  by  bit.  To  remove  the  brain,  it  will  be  necessary  to  cut 
through  the  tough  dura  mater  that  covers  it. 

Removing  this,  there  will  be  found  an  inner  covering,  the  pia  mater, 
a  membrane  richly  supplied  with  blood  tubes,  from  which  the  brain 
gets  its  nourishment.  After  the  dura  mater  has  been  removed,  the 
anterior  end  of  the  brain  may  be  gently  lifted  with  the  handle  of  the 
scalpel  and  the  under  surface  studied,  following  the  description  of 
the  cranial  nerves. 

Preservation  of  the  Brain.  —  The  brain  may  be  studied  while  it 
is  fresh,  but  it  is  more  easily  handled  after  it  has  been  hardened.  Lay 
the  brain  in  weak  alcohol,  about  25  per  cent.  It  should  rest  on  a  layer 
of  cotton,  otherwise  it  may  be  very  much  flattened  by  its  own  weight. 
Later  transfer  it  to  50  per  cent  alcohol,  and  then  to  75  per  cent.  When 
it  is  well  hardened,  it  may  be  sliced  with  a  sharp  scalpel  as  directed. 
A  better  and  quicker  method  is  to  use  a  solution  of  alcohol  and  forma- 


THE  BRAIN  237 

lin  as  follows  :   95  per  cent  alcohol,  60  parts  ;   .2  per  cent  formol,  40 
parts.     The  liquid  need  not  be  changed  if  used  in  sufficient  volume. 

The  Brain  of  the  Rabbit  {Alcoholic  Specimen}.  —  The  brain  of 
a  cat  or  dog  is  better,  being  larger.  Take  a  brain  well  hardened,  and 
review  the  parts  as  named  above.  It  is  very  desirable  to  have  a  speci- 
men in  which  the  arteries  have  been  injected. 

1 .  Press  down  the  cerebellum  to  see  the  deep  groove  between  it  and 
the  cerebrum.      The  thin  membrane  covering  the  brain  and  dipping 
into  the  groove  is  the  pia  mater. 

2.  Press  down  the  spinal  bulb  and  tear  away  the  pia  mater  where 
it  passes  from  the  cerebellum  to  the  spinal  bulb.     Note,  between  the 
bulb  and  the  cerebellum,  a  space  covered  by  a  thin  membrane.     Cut 
through  this  membrane ;  the  cavity  is  the  fourth  ventricle  of  the  brain. 
Observe  the  two  ridges  bounding  the  sides  of  the  fourth  •ventricle.     At 
the  point  of  their  divergence,  observe  the  opening  of  the  central  canal 
of  the  spinal  cord. 

3.  Gently  separate  the  cerebral  hemispheres,  and  note  the  trans- 
verse band  of  white  fibers  connecting  them. 

4.  Examine  the  under  surface  of  the  brain,  and  find  the  roots  of  the 
cranial  nerve. 

The  Cranial  Nerves  and  their  Functions.  —  i.   The 

olfactory  lobes  extend  forward  under  the  fore  part  of  the 
cerebral  hemispheres.     They  are  the  nerves  of  smell. 

2.  The  optic  netves,  or  nerves  of  sight,  join  each  other 
before  reaching  the  brain.     Only  the  first  and  second  pairs 
of  cranial  nerves  directly  enter  the  cerebrum. 

3.  Back  of  the  optic  nerves,  near  the  middle  line,  is  the 
third  pair  of  nerves.     The  third,  fourth,  and  sixth  pairs 
of  cranial  nerves  control  the  muscles  of  the  eyeballs. 

4.  The  fourth  pair   extend  up   on  each  side  into  the 
groove  between  the  cerebrum  and  the  cerebellum. 

5.  Back  of  these  is  the  larger  fifth  pair,  the  trigeminal. 
This  pair  supplies  part  of  the  face,  and  sends  branches  to 
the  teeth.     It  is  the  nerve  affected  in  neuralgia  of  the 
face.     Besides  being  the  nerve  of  sensation  for  most  of  the 


238 


PHYSIOLOGY. 


head  and  face,  this  nerve  has  motor  fibers  which  control 
the  muscles  of  mastication.  Unlike  the  other  cranial 
nerves,  the  trigeminal  resembles  the  spinal  nerves  in 
having  two  roots,  one  sensory,  the  other  motor. 


Optic 
(Sight) 


I,  Olfactory 

(Smell) 


Eye  Motor, 
3,4,6 


Hypoglossai, 
12  (Tongue 
Motor) 


5,  Trigeminal 
(Face 
Sensation) 


II,  Spinal 
Accessory 


Fig.  77.    The  Base  of  the  Brain,  showing  the  Origin  of  the  Cranial  Nerves. 


6.  Back  of  and  inside  of  the  fifth  pair  is  the  sixth  pair. 

7.  The  nerves  of  the  seventh  pair  are  larger,  and  are 
farther  back  and  outward.     These  are  the  facial  nerves, 
and  control  the  muscles  of  the  face  and  the  facial  expres- 


sion. 


THE  BRAIN. 


239 


8.  Close   to    the    seventh    are    the    eighth,   or   auditory 
nerves. 

9.  The  ninth,  tenth,  and  eleventh  arise  close  together, 
farther  back  and  well  up  on  the  sides  of  the  spinal  bulb. 
The  ninth  supplies  the  back  of  the  tongue  and  the  pharynx, 
and  is   called   the  glosso-pJiaryngeal  nerve.     It  gives   the 
sense  of  taste  from  the  base  of  the  tongue. 

Cerebrum 


Fig.  78.     Vertical  Section  of  Brain. 

10.  The  tenth  pair,  or  vagus  nerves  pass  down  out  of 
the  brain   cavity,  give  off  branches  to   the   pharynx  and 
larynx,  and  are  distributed  to  the  heart,  lungs,  and  stomach. 
The  vagus  nerves  are  so  widely  distributed  that  their  func- 
tions cannot  be  briefly  stated. 

11.  The    eleventh    pair   arise   in    part  from   the   spinal 
cord  outside  of  the  cranial  cavity,  enter  the  skull,  and  pass 


240 


PHYSIOLOGY. 


out   again    to    supply    certain    muscles   of   the    neck   and 
shoulders. 

12.  The  last  pair  of  cranial  nerves,  the  twelfth,  arise 
near  the  middle  line  of  the  spinal  bulb.  This  pair  supply 
the  muscles  of  the  tongue,  and  are  called  the  hypoglossal 
nerves. 

Brain  composed  of  Two  Hemispheres.  —  It  will  be 
observed  that  the  brain,  like  the  spinal  cord,  consists  of 
two  lateral  parts.  Cutting  sections  of  the  brain  length- 
wise and  crosswise  shows  that  the  outer  part  is  made  up 
of  gray  matter  and  the  inner  part  of  white  matter.  The 
gray  matter  is  composed  of  cells  essentially  similar  to  those 
of  the  spinal  cord,  while  the  white 
matter  of  the  inner  part  is  composed 
of  white  fibers  like  those  of  the  outer 
part  of  the  spinal  cord,  or  like  the 
nerves. 

Brain  Convolutions  and  Intelli- 

.  79.  Pyramidal  Nerve  gence.  —  The  brain  of  the  rabbit  has 
^wer  convolutions  than  that  of  the 
cat,  and  is  nearly  smooth.  In  gen- 
eral, the  lower  animals  have  fewer  convolutions,  and  the 
lower  races  of  mankind  have  smoother  brains  than  the 
higher  races.  In  the  earlier  stages  of  development  man's 
brain  is  smoother,  but  with  growth  the  convolutions 
appear,  and  increase  in  number  with  the  growth  of  the 
brain.  As  we  know  that  intelligent  action  depends  on 
the  gray  matter  of  the  surface  of  the  brain,  we  infer  that 
to  accommodate  its  increase  in  the  brain  case  it  is  thrown 
into  folds,  as  the  surface  of  the  lining  of  the  intestines-  is 
increased  by  folds  and  villi. 


THE  BRAIN. 


241 


Gray  and  White  Matter  of  the  Brain.  —  The  gray 
matter  of  the  convolutions  of  the  adult  human  brain  is 
about  one  fifth  of  an  inch  thick,  the  larger  part  of  the 
brain  consisting  of  the  white  matter.  Sections  will  show 
that  there  are  several  masses  of  gray  matter  in  the  brain 
deeper  than  the  con- 
volutions. These  ^.AdfeA^  Gray  Matter 

are  the  ganglia  of 
the  brain.  The 
white  fibers  inside 
the  brain  connect 
the  gray  matter  of  Gangiia 
the  convolutions 
and  these  ganglia 
with  all  parts  of 
the  body  through 
the  spinal  cord. 


Cerebrum 


Cerebellum 


Fig.  80.    Diagram  of  -the   Brain,   showing  the  Spinal 
Cord,  Ganglia,  and  Course  of  the  Fibers. 


Neuroglia.  — The  brain  consists  of  nerve  cells  and  nerve 
fibers,  bound  together  and  supported  by  a  form  of  connec- 
tive tissue  called  neuroglia. 

The  Cerebrum  and  its  Functions.  —  If  the  cerebral 
hemispheres  are  removed  from  a  frog,  he  will  sit  up  about 
as  before,  but  seems  to  pay  little  attention  to  what  is  going 
on  around  him.  If  placed  on  his  back;  he  will  turn  over 
and  sit  up.  If  pinched,  he  may  jump  away,  and  may  show 
that  he  can  see  by  avoiding  anything  that  may  come  in  his 
way.  If  placed  in  the  water,  he  will  swim,  and  if  he  swims 
against  anything  that  he  can  climb  upon,  will  do  so  and 
remain  quiet.  If  placed  on  a  board,  and  the  board  be 
slowly  tilted,  he  will  move  along  and  keep  his  equilibrium, 
climbing  over  the  end  of  the  board  if  necessary  to  keep  his 
balance.  If  left  alone,  he  will  not  move,  but  will  die  in 


242 


PHYSIOLOGY. 


his  tracks,  though  he  will  eat  food  if  it  is  put  in  his  mouth. 
He  seems  to  have  lost  the  power  of  willing  to  do  anything, 
or  what  we  call  the  power  of  volition.  He  originates  no 
action. 

A  Pigeon  with  Cerebrum  Removed.  —  A  pigeon  with 
its  cerebrum  removed  acts  in  about  the  same  way.  It 
remains  quiet,  stupid,  paying  no  attention  to  ordinary 


f- Spinal  Cord 

-  1st  Spinal  Nerve 

-  2d  Spinal  Nerve 


Fig.  81.    Diagram  of  the  Cranial  Nerves  and  Sense  Organs. 

events.  A  sudden  loud  noise  may  cause  it  to  start.  If  its 
tail  be  pulled,  it  moves  forward  to  regain  its  balance.  If 
thrown  in  the  air,  it  flies  for  a  distance.  It  swallows  food 
placed  in  its  mouth,  but  would  starve  surrounded  by  food. 


THE   URAfN.  243 

Placed  on  its  back,  it  will  right  itself,  but  it  does  not  show 
the  usual  degree  of  intelligence  and  will  power. 

Function  of  the  Cerebral  Cortex.  —  "  Experimentally, 
we  learn  that  after  the  removal  of  the  cortex  (gray  matter) 
an  intelligent  animal  is  reduced  to  the  state  of  a  non-intelli- 
gent automaton,  responding  indeed  to  stimuli,  internal  as 
well  as  external,  but  failing  to  interpret  the  significance  of 
present  events  in  accordance  with  bygone  experience.  A 
brainless  dog  is  stupid ;  he  may  see  a  bone  in  front  of  his 
eyes  without  showing  signs  that  he  knows  the  meaning  of 
a  bone  or  the  use  to  which  it  may  be  put ;  he  may  hear  the 
crack  of  a  whip,  but  he  no  longer  shows  signs  of  fear, 
for  he  does  not  remember  its  sting ;  his  former  purposeful 
behavior  has  entirely  disappeared  ;  in  short,  he  has  lost 
memory  and  judgment."  -WALLER. 

The   Center   of   Sensations   itself   Insensible.  —  The 

gray  matter  of  the  outside  of  the  brain  is  the  central  organ 
of  intelligent  sensation  and  motion.  The  functions  of  voli- 
tion, of  consciousness,  of  intelligence,  seem  to  reside  in,  or 
rather  to  depend  upon  the  activities  of,  the  cells  of  the 
gray  matter  of  the  convolutions  of  the  cerebrum.  This  we 
have  learned  from  experiments  on  the  lower  animals,  and 
from  accidents  and  disease  in  the  case  of  man.  All  sensa- 
tion seems  to  be  in  the  gray  matter  of  the  convolutions  of 
the  cerebrum,  and  yet  it  is  itself  insensible;  it  may  be  cut 
and  cause  no  sensation.  But  when  the  nerve  impulses 
from  the  various  parts  of  the  body  reach  the  gray  matter 
of  the  cerebrum  they  rouse  the  cells  here  to  an  activity 
that  gives  us  what  we  call  sensation.  It  is  never  a  sensa- 
tion until  it  reaches  this  part  and  is  properly  interpreted. 

Crossed  Control  of  the  Body. — While  each  hemisphere 
mainly  controls  the  muscles  of  the  opposite  half  of  the 


244 


PHYSIOLOGY. 


body,  it  also,  in  part,  has  control  of  its  own  side.  Paralysis 
of  one  side  (hemiplegia)  is  due  to  injury  of  the  opposite 
cerebral  hemisphere. 

Location  of  Brain  Functions.  —  Much  has  been  learned 
of  late  years  as  to  the  location  of  special  functions  in  the 
brain.  Many  of  the  motor  centers  have  been  determined 

CENTRAL   FISSURE 
MOTOR  AREA  x'' 


FISSURE  OF  SILVIU8 


Fig.  82.     Location  of  Brain  Functions. 

in  the  following  manner :  In  some  of  the  lower  animals 
the  brain  has  been  exposed,  and  on  stimulating  certain 
portions  with  an  electric  current  the  movements  that  fol- 
lowed were  noted.  In  monkeys,  "  particular  movements 
of  the  arm,  forearm,  hand,  and  thumb  can  be  produced  by 
excitation  of  particular  spots,  almost  as  regularly  as  definite 
notes  can  be  sounded  on  a  piano  by  touching  particular 


THE  BRAIN.  245 

keys."  In  the  case  of  man  we  infer  that  there  is  a  similar 
location,  and  many  cases  of  accident  and  disease  have 
helped  in  locating  the  functions.  But  these  areas  are  not 
sharply  defined. 

Left  Hemisphere  Better  Developed.  —  The  "speech 
center"  is  in  the  left  hemisphere;  the  right  eye  and  ear, 
which  connect  with  the  left  brain,  are  better  developed 
than  the  left,  and  in  general  the  left  hemisphere  seems 
superior  (in  right-handed  persons)  to  the  right. 

Location  of  Centers  of  Sensation.  —  It  is  not  so  easy 
to  locate  the  centers  of  sensation  as  those  for  motion.  For 
we  can  see  the  resulting  motion,  but  a  sensation  can  only 
be  felt  by  the  individual  in  whom  it  occurs.  Still,  some  of 
the  sensation  centers  have  been  located,  and  it  is  likely 
that  in  time  we  shall  know  much  more  on  this  subject. 
The  accompanying  diagram  shows  some  of  these  centers. 

The  Functions  of  the  Cerebellum.  —  The  cerebellum 
is  the  center  for  regulating  the  actions  of  the  skeletal  mus- 
cles. When  we  walk  or  run,  or  even  stand  still,  a  number 
of  muscles  must  act,  and  act  in  concert.  The  nerve  im- 
pulses originate  in  the  cerebrum,  but  the  cerebellum  is  the 
center  for  harmonizing  the  action  of  these  various  muscles, 
or  coordinating  them.  When  the  cerebellum  has  been  re- 
moved from  a  pigeon  the  bird  flutters,  and,  while  possess- 
ing the  power  to  move,  does  not  seem  capable  of  any 
regular  and  orderly  movement.  There  is  no  loss  of  intelli- 
gence, no  paralysis.  Of  course,  in  this  experiment  there 
is  great  disturbance  of  the  system,  and  perhaps  too  much 
is  inferred  from  it. 

Functions  of  the  Spinal  Bulb.  —  The  spinal  bulb  is  the 
connection  between  the  spinal  cord  and  the  brain.  The 


246  rUYSIOLOGY. 

bulb  may  be  said  to  be  that  part  of  the  spinal  cord  which 
is  within  the  cranium.  It  is  enlarged,  hence  its  name, 
tpinal  bulb.  From  it  arise  all  the  cranial  nerves  except 
the  first  five  pairs.  The  spinal  bulb  is  also  the  center  for 
the  control  of  respiration,  of  circulation,  of  deglutition,  and 
perhaps  for  many  other  processes. 

Brain  Work  and  Brain  Rest.  —  Sleep  is  not  merely 
rest  for  the  body ;  it  should  be  complete  rest  for  the  brain. 
In  so  far  as  there  are  dreams,  it  would  seem  to  indicate  a 
partial  activity  ;  that  is,  incomplete  rest.  The  brain  worker 
especially  needs  plenty  of  sleep ;  excellent  authorities  say 
at  least  eight  or  nine  hours.  The  brain,  like  the  muscles, 
needs  exercise,  and  it  also  needs  regular  periods  of  rest. 
If  a  nerve  cell  is  not  kept  active  by  the  passage  of  nerve 
impulses  through  it,  it  usually  atrophies,  and  may  de- 
generate. 

Sleeplessness.  —  Intense  brain  work,  without  sufficient 
sleep,  is  likely  to  lead  to  sleeplessness,  as  when  one  has 
some  subject  of  special  study  in  hand  and  either  will  not 
or  cannot  throw  it  off.  Perhaps  inventors  are  as  prone  to 
this  sort  of  trouble  as  any  one  class  of  men.  Keeping  the 
blood  continually  in  the  brain,  or  in  any  organ,  is  likely  to 
lead  to  a  permanent  congestion  or  inflammation  that  may 
cause  serious,  if  not  fatal,  results. 

Fatigue. — It  is  stated  that  brain  workers  need  more 
sleep  than  those  who  work  chiefly  with  the  muscles.  Fa- 
tigue of  the  voluntary  muscles  is  much  more  a  matter  of 
nervous  than  of  muscular  origin.  When  one  is  completely 
"  tired  out,"  as  he  would  say,  if  his  mind  can  be  aroused, 
as  by  some  excitement,  he  will  be  found  able  to  expend  a 
good  deal  more  muscular  energy.  So,  too,  many  persons 
of  slight  muscular  build,  but  of  great  "  will  power,"  are 


THE  BRAIN.  247 

able  to  do  more  work  with  the  muscles  than  others  with 
larger  muscles  and  less  will.  During  fatigue  the  cell  bodies 
are  found  to  decrease  in  size,  but  there  is  no  discernible 
change  in  nerve  fibers  as  a  result  of  fatigue. 

Control  of  Mind.  —  But  the  brain  worker  should  not 
only  be  able  to  sleep  regularly  and  long  enough ;  he  ought 
to  be  able  to  throw  off  his  mind  any  subject,  and  take  rest 
while  he  is  awake.  If  one  allows  himself  to  think  about 
mental  work  while  eating,  the  process  of  digestion  will  not 
go  on  well. 

Habit  of  Resting  the  Brain.  —  The  student  should  ac- 
quire the  power  and  cultivate  the  habit  of  having,  so  far 
as  possible,  regular  hours  for  work,  and  of  completely 
throwing  aside  his  work  and  worry  at  stated  times.  In 
seeking  recreation  it  is  well  to  choose  that  which  will 
necessitate  giving  the  attention  to  something  entirely  dif- 
ferent from  the  daily  work.  For  this  reason  chess  may 
be  no  real  recreation  for  the  student,  while  a  game  of 
tennis,  boxing,  or  other  competitive  exercise  is  likely  to 
accomplish  this  very  desirable  object.  A  walk  may  put 
the  muscles  into  play,  but  if  the  mind  is  still  intent  upon 
the  line  of  work  maintained  throughout  the  day,  the  exercise 
may  prove  of  little  benefit.  He  may  return  more  tired 
than  when  he  set  out.  The  exhilaration  of  horseback  rid- 
ing may  prove  far  better,  though  perhaps  involving  much 
less  muscular  exertion. 

Nervous  Tissue  least  affected  by  Starvation.  —  It  is 
worthy  of  note  that  in  fasting  the  nervous  tissue  is  less 
reduced  than  any  other  tissue,  being  scarcely  diminished 
by  complete  starvation. 

Blood  Supply  of  the  Brain.  —  Blood  is  supplied  to  the 
brain  through  four  arteries :  the  right  and  left  internal 


248  PHYSIOLOGY. 

carotid  arteries,  and  the  right  and  left  vertebral  arteries. 
These  arteries  are  so  connected  by  cross-branches  that 
if  any  three  of  them  should  be  compressed,  or  the  blood 
flow  in  them  otherwise  stopped,  the  fourth  would  still  be 
able  to  give  the  brain  blood  enough  for  its  work.  When 
the  brain  is  more  active  it  receives  a  larger  supply  of 
blood.  During  sleep  it  is  paler. 

Fainting.  —  If  the  supply  of  blood  to  the  brain  is  shut 
off,  unconsciousness  quickly  follows.  In  the  ordinary 
faint  the  blood  supply  has  been  reduced,  owing  to  the 
diminution  of  the  blood  pressure  or  heart's  force.  It  may 
be  due  to  inhibition  of  the  heart  from  some  emotion,  or 
bad  odor,  as  in  a  close  room ;  severe  pain  may  be  the 
cause ;  a  blow  over  the  pit  of  the  stomach  may  stop  the 
heart  by  reflex  action.  Fresh  air  should  be  supplied, 
and  the  body  laid  flat  on  the  back.  This  position  makes 
it  easier  for  the  blood  to  reach  the  brain  and  restore 
consciousness.  Smelling  salts  (or  ammonia)  may  stimu- 
late respiration  and  circulation.  Sprinkling  a  little  cold 
water  on  the  face  may  have  the  same  effect,  but  it  is 
not  necessary  to  pour  a  large  quantity  of  water  over  the 
person.  Rubbing  the  limbs  toward  the  heart  promotes 
the  flow  of  blood,  and  tends  to  start  the  heart  to  activity. 

Apoplexy.  —  Apoplexy  is  caused  by  rupture  of  a  blood 
tube  and  the  formation  of  a  clot  that  presses  on  the  brain. 

Meningitis.  —  Meningitis  is  an  inflammation  of  the 
membranes  immediately  surrounding  the  brain  or  spinal 
cord  or  both. 

The  Water  Cushion  of  the  Brain.  —  Between  the  coats 
surrounding  the  brain  and  spinal  cord  there  is  a  layer  of 
liquid,  comparable  to  that  around  the  heart  or  lungs. 
When  an  undue  amount  of  blood  is  sent  to  the  brain, 


THE  BRAIN.  249 

it  is  supposed  that  part  of  the  cerebrospinal  fluid  is 
pressed  out  into  the  spinal  cavity,  thus  relieving  the  pres- 
sure in  the  brain  cavity. 

Relative  Activity  of  Gray  and  White  Matter.  —  The 

gray  matter  is,  physiologically,  more  active  than  the  white, 
and  in  keeping  with  this  is  the  fact  that  the  capillary 
network  is  closer  in  the  gray  matter  than  in  the  white. 
This  is  true  of  the  spinal  cord  as  well  as  of  the  brain. 

READING.  —  Brain-work    and    Over-work,    Wood ;     The 
Brain  and  its  Functions,  Luys. 


Summary.  —  i .   The  outside  of  the  brain  consists  of  gray  matter, 
the  inside  of  white  matter. 

2.  The  twelve  pairs  of  cranial  nerves  are  distributed  to  the  head, 
with  the  exception  of  the  tenth  and  part  of  the  eleventh. 

3.  The  cranial  nerves  include  all  the   special  senses   but  that  of 
touch. 

4.  Each  hemisphere  of  the  brain  is  connected  with,  and  has  chief 
control  of,  the  opposite  half  of  the  body. 

5.  The  gray  matter  of  the  cerebrum  is  the  seat  of  the  will,  sensation, 
thought,  and  emotion. 

6.  The  cerebellum  regulates  voluntary  motion. 

7.  Many  of  the  cerebral  functions  have  been  located. 

8.  The  brain  needs  rest.     In  sleep  less  blood  flows  through  the 
brain. 

9.  Work  reduces  the  size  of  nerve  cells.     During  rest  they  increase 
again. 

Questions.  —  i.   Is  there  any  special  reason  why  the  "speech  cen- 
ter "  should  be  in  the  left  cerebral  hemisphere  ? 

2.  Why  does  a  light  lunch  sometimes  enable  one  to  go  to  sleep 
after  mental  work  ? 

3.  Why  is  it  uncomfortable  to  hold  the  head  down  ? 

4.  How  does  the  nervous  system  resemble  a  telegraph  system  ?     In 
what  respects  are  the  two  unlike  ? 

5.  Name  some  remedies  for  sleeplessness. 


CHAPTER    XVI. 
EFFECTS  OF   ALCOHOL  ON  THE   NERVOUS   SYSTEM. 

[Treatise  on  Hygiene,  STEVENSON  and  MURPHY.] 

"  THE  physiological  effects  of  alcohol  which  have  been 
considered  are  quite  subsidiary  to  its  effects  on  the  central 
nervous  system,  as  there  is  no  doubt  that  it  is  for  this 
effect  on  the  brain  that  alcoholic  beverages  are  so  univer- 
sally taken  by  mankind.  The  first  effect  that  alcohol  has 
on  the  brain  is  that  of  a  stimulant,  and  it  probably  acts  as 
such  in  two  ways ;  namely,  by  increasing  the  circulation 
of  blood  through  the  brain,  which  is  thus  roused  to  greater 
vigor,  and  by  directly  stimulating  the  nerve  cells  of  the 
nerve  centers.  This  stimulating  effect  is  observed  chiefly 
after  medium  or  dietetic  doses,  and  its  result  is  seen  in 
many  individuals  by  an  increase  of  mental  and  bodily 
activity,  and  of  acuteness  of  perception  by  the  special 
senses.  This  beneficial  physiological  effect  is,  however, 
soon  replaced  by  poisonous  symptoms  if  the  dietetic  doses 
are  too  often  repeated,  or  a  large  quantity  of  alcohol  is 
taken  at  once ;  for  alcohol  then  becomes  a  depressant  and 
paralyzer  of  the  central  nervous  system,  and  symptoms 
of  intoxication  appear.  This  depressant  effect  is,  as  Brun- 
ton  points  out,  one  of  progressive  paralysis.  The  higher 
centers  of  the  brain  are  first  affected,  then  the  lower. 
The  perceptive  centers  are  paralyzed,  so  that  correct 
judgment  is  no  longer  possible,  while  the  emotions  are 
uncontrolled  and  thrown  out  of  working  gear,  fits  of  bois- 
terous hilarity  and  of  emotional  depression  being  common 

250 


EFFECTS   OF  ALCOHOL    ON  NERVOUS  SYSTEM.      251 

symptoms.  Speech  becomes  disordered,  and  symptoms 
of  incoordination,  due  probably  to  an  effect  on  the  cere- 
bellum, appear.  The  respiratory  center  in  the  medulla 
then  becomes  affected,  and  at  this  stage  there  is  coma 
with  stertorous  breathing,  while  the  action  of  the  heart 
still  continues,  even  after  respiration  has  stopped.  There 
can  be  no  question  that  alcohol  taken  in  sufficient  quanti- 
ties to  depress  the  higher  centers  of  the  brain  does  an 
infinite  amount  of  harm." 

Dr.  Crothers,  author  of  Diseases  of  Inebriety,  says,  "  I 
have  often  been  made  impatient  in  listening  to  the  lecturer 
presenting  the  '  scientific  aspects  of  the  alcohol  question ' 
to  an  audience,  to  see  him  illustrate  extensively  with 
charts,  and  spend  hours  to  show  the  effects  of  alcohol 
upon  the  coats  of  the  stomach,  and  upon  the  structure  of 
the  liver  and  the  kidneys,  and  never  allude  once  to  the 
brain ;  when  the  fact  is,  alcohol's  principal  effect  is  upon 
this  organ,  and  the  functions  of  this  organ  so  far  transcend 
the  functions  of  all  the  others,  that  I  might  say,  there  is 
no  comparison." 

Some  authors  hold  that  the  alterations  in  the  tissues  by 
alcoholic  drinks  result  from  the  injury  to  the  nerve  centers 
that  preside  over  these  tissues  ;  for  their  nutrition  depends 
not  merely  on  the  direct  effect  of  the  blood  and  lymph 
supply,  but  also  upon  the  direct  influences  of  the  nerve 
centers ;  they  even  go  so  far  as  to  maintain  that  there  is  a 
special  set  of  nerve  fibers  devoted  to  the  control  of  the 
nutrition  of  the  cells,  and  these  nerve  fibers  they  call 
"trophic  nerves"  or  "trophic  fibers." 

"  It  is  clear  that  the  nervous  centers,  independently  of 
the  ill  effects  on  their  nutrition  by  the  blood  changes, 
have  a  certain  chemical  attraction  for  alcohol,  which 
accordingly  is  found  in  their  tissue."  —CROTHERS. 


252 

Dr.  Crothers,  in  common  with  many  physicians,  regards 
inebriety  as  a  disease. 

Dr.  Clum  in  his  work  entitled  Inebriety,  its  Causes,  its 
Results,  its  Remedy,  says :  "  The  most  important  part  of 
man  is  his  nervous  system  ;  the  cerebrospinal,  sympathetic, 
and  vasomotor  being  intimately  interwoven  and  connected, 
composing  the  whole.  The  great  nervous  center,  the  brain, 
with  its  hemispheres,  its  gray  and  white  matter,  is  the 
most  complex  of  all  complexities.  The  nerve  fibers  not 
only  connect  every  cell  with  every  other  cell,  but  unite  all 
nervous  structures  into  one,  making  the  entire  body  a 
complete  whole,  and  forming  close  and  direct  sympathy 
between  the  intellect  and  the  physical  organization. 

"  The  mind  and  body  are  so  intimately  connected  that 
exhausting  excess  of  either  acts  and  reacts  on  the  other. 
Excessive  work,  either  intellectual  or  physical,  the  sudden 
loss  of  property,  intense  disappointment,  great  trouble,  un- 
requited affections,  etc.,  may  impart  a  shock  to  the  senses 
through  the  mind,  which,  extending  to  the  molecules  of 
the  brain,  disturbs  their  normal  action ;  and  a  sufferer 
thus  worn  and  debilitated*  with  the  cares  of  life,  with  an 
enfeebled  will  power,  the  result  of  nervous  exhaustion, 
experiences  a  craving  for  some  form  of  stimulant  to  *  brace 
him  up.'  He  is  on  the  verge  of  inebriety,  or  of  insanity, 
or  both,  and  if  he  indulges  in  alcoholic  beverages  he 
becomes  an  inebriate.  Any  disease  inherited  or  acquired, 
acting  either  directly  or  indirectly  upon  the  nervous  system, 
may  act  as  the  predisposing,  exciting,  or  complicating  and 
protracting  cause  of  alcoholic  inebriety." 

"  Inebriety  is  often,  too  often,  observed  to  flourish  in 
the  richest  and  most  promising  soil.  The  clergyman,  the 
lawyer,  the  editor,  the  student,  and  all  others  -who  use 
their  intellectual  faculties  to  excess,  as  well  as  the  mechanic, 


EFFECTS   OF  ALCOHOL    ON  NERVOUS  SYSTEM.      253 

the  laborer,  and  those  who  excessively  exert  their  physical 
system,  have  unnatural  longings  for  something  to  restore 
the  exhausted  energies  of  mind  and  body. 

"The  excessive  worry  of  one  man,  the  exhausting  ex- 
cesses of  another,  and  the  overwork  of  others,  lead  to 
organic  lesions  and  nervous  defects,  and  the  disease 
inebriety,  an  ungovernable  craving  for  alcoholic  drinks,  is 
the  result. 

"  When  a  man  drinks  to  excess,  even  though  forced  to 
do  so  by  a  diseased  nervous  system,  Christian  communities 
usually  brand  him  as  a  criminal,  as  an  outcast,  and  say, 
'  We  have  no  sympathy  for  you ;  stop  drinking  and  be  a 
man,'  when  in  reality  the  man  should  be  cared  for,  and 
treated  as  other  diseased  human  beings.  The  fact  that  the 
desire  for  alcoholic  drinks  is  often  a  disease  which  may  be 
either  inherited  or  acquired  is  overlooked  by  those  who 
condemn  the  drunkard.  Our  ancestors  have  for  ages  been 
addicted  to  habits  of  intoxication,  and  we,  their  descend- 
ants, are  tainted  with  the  disease  inebriety." 

MORAL  DETERIORATION   PRODUCED   BY  ALCOHOL. 

[PROFESSOR  H.  NEWELL  MARTIN.] 

"  One  result  of  a  single  dose  of  alcohol  is  that  the  con- 
trol of  the  will  over  the  actions  and  emotions  is  temporarily 
enfeebled ;  the  slightly  tipsy  man  laughs  and  talks  loudly, 
says  and  does  rash  things,  is  enraged  or  delighted  without 
due  cause.  If  the  amount  of  alcohol  be  increased,  further 
diminution  of  will  power  is  indicated  by  loss  of  control 
over  the  muscles.  Excessive  habitual  use  of  alcohol 
results  in  permanent  overexcitement  of  the  emotional 
nature,  and  enfeeblement  of  the  will;  the  man's  highly 
emotional  state  exposes  him  to  special  temptations,  to 


254 

excesses  of  all  kinds,  and  his  weakened  will  decreases  the 
power  of  resistance ;  the  final  outcome  is  a  degraded 
moral  condition.  He  who  was  prompt  in  the  performance 
of  duty  begins  to  shirk  that  which  is  irksome,  energy  gives 
place  to  indifference,  truthfulness  to  lying,  integrity  to 
dishonesty ;  for  even  with  the  best  intentions  in  making 
promises  or  pledges  there  is  no  strength  of  will  to  keep 
them.  In  forfeiting  the  respect  of  others,  respect  for  self 
is  lost  and  character  is  overthrown.  Meanwhile  the  pas- 
sion for  drink  grows  absorbing ;  no  sacrifice  is  too  costly 
which  secures  it.  Swift  and  swifter  is  now  the  downward 
progress.  A  mere  sot,  the  man  becomes  regardless  of 
every  duty,  and  even  incapacitated  for  any  which  momen- 
tary shame  may  make  him  desire  to  perform. 

"  For  such  a  one  there  is  but  one  hope, —  confinement 
in  an  asylum,  where,  if  not  too  late,  the  diseased  craving 
for  drink  may  be  gradually  overcome,  the  prostrated  will 
regain  its  ascendency,  and  the  man  at  last  gain  the  victory 
over  the  brute." 

NARCOTICS. 

Definitions  of  Narcotics.  —  Gould's  Dictionary  of  Medi- 
cine, one  of  the  very  best  authorities,  thus  defines  narcotic  : 
"A  drug  that  produces  narcosis"  and  narcosis,  as  "the 
deadening  of  pain,  or  the  production  of  incomplete  or  com- 
plete anesthesia  by  the  use  of  narcotic  agents,  such  as  the 
use  of  anesthetics,  opium,  and  other  drugs."  It  is  common, 
however,  to  treat  of  chloroform,  ether,  chloral  hydrate,  etc., 
in  a  group  by  themselves  under  the  designation  Anesthetics. 

The  Century  Dictionary  thus  defines  narcotic  :  "  A  sub- 
stance which  directly  induces  sleep,  allaying  sensibility  and 
blunting  the  senses,  and  which,  in  large  quantities,  pro- 
duces narcotism  or  complete  insensibility.  Opium,  Cauna- 


EFFECTS   OF  ALCOHOL   ON  NERVOUS  SYSTEM.      255 

bis  Indica,  hyoscyamus,  stramonium,  and  belladonna  are 
the  chief  narcotics,  of  which  opium  is  the  most  typical. 
Direct  narcotics  .  .  .  either  produce  some  specific  effect 
upon  the  cerebral  gray  matter,  or  have  a  very  decided 
action  on  the  blood  supply  of  the  brain." 

Some  authorities  class  alcohol  with  the  narcotics. 


OPIUM. 

Opium.  —  Opium  is  the  dried  and  thickened  juice  of  the 
head,  or  capsule,  of  a  species  of  poppy.  Incisions  are 
made  in  the  partially  ripened  heads ;  the  milky  juice  ex- 
udes ;  after  about  twenty-four  hours  the  partially  dried 
and  thickened  material  is  scraped  off  with  a  dull  knife. 
Most  of  the  opium  comes  to  this  country  from  Smyrna, 
with  a  smaller  quantity  from  Constantinople.  As  gathered 
it  is  a  reddish  brown,  sticky  substance  of  peculiar  odor. 
It  is  soluble  in  water,  alcohol,  and  dilute  acids,  to  all  of 
which  it  gives  a  deep  brown  color.  It  is  a  very  complex 
substance,  but  the  chief  constituent  is  morphia,  or  mor- 
phine, to  which  the  properties  of  opium  are  due.  One 
fourth  of  a  grain  of  morphine  is  equal  to  a  grain  of  opium 
of  the  average  strength.  "  Opium  was  known  to  the 
Greeks,  but  was  not  much  used  before  the  seventeenth 
century ;  at  present  it  is  the  most  important  of  all  medi- 
cines, and  its  applications  the  most  multifarious,  the  chief 
of  them  being  for  the  relief  of  pain  and  the  production  of 
sleep.  Its  habitual  use  is  disastrous  and  difficult  to  break 
up.  It  is  classed  as  a  stimulant  narcotic,  acting  almost 
exclusively  on  the  central  nervous  system  when  taken  in- 
ternally ;  in  large  quantities  it  is  a  powerful  narcotic  poison, 
resulting  in  a  coma  characterized  by  great  contraction  of 
the  pupils,  insensibility,  and  death."  —  Century  Dictionary. 


256  PHYSIOLOGY. 

Properties  and  Uses  of  Opium.  —  The  United  States 
Dispensatory  makes  the  following  statements  as  to  its 
medical  properties  and  uses :  "  Opium  is  a  stimulant  nar- 
cotic. Taken  by  a  healthy  person  in  a  moderate  dose,  it 
increases  the  force,  fullness,  and  frequency  of  the  pulse, 
augments  the  temperature  of  the  skin,  invigorates  the 
muscular  system,  quickens  the  senses,  animates  the  spirits, 
and  gives  new  energy  to  the  intellectual  faculties.  Its  op- 
eration, while  thus  extending  to  all  parts  of  the  system,  is 
directed  with  peculiar  force  to  the  brain,  the  functions  of 
which  it  excites  sometimes  even  to  intoxication  or  delirium. 
In  a  short  time  this  excitation  subsides  ;  a  calmness  of  the 
corporeal  actions,  and  a  delightful  placidity  of  mind  suc- 
ceed ;  and  the  individual,  insensible  to  painful  impressions, 
forgetting  all  sources  o'f  care  and  anxiety,  submits  himself 
to  a  current  of  undefined  and  unconnected  but  pleasing 
fancies,  and  is  conscious  of  no  other  feeling  than  that  of  a 
quiet  and  vague  enjoyment.  At  the  end  of  half  an  hour 
or  an  hour  from  the  administration  of  the  narcotic,  all  con- 
sciousness is  lost  in  sleep.  The  soporific  effect,  after  hav- 
ing continued  for  eight  or  ten  hours,  goes  off,  and  is  often 
succeeded  by  more  or  less  nausea,  headache,  tremors,  and 
other  symptoms  of  diminished  or  irregular  nervous  action, 
which  soon  yield  to  the  recuperative  energies  of  the  sys- 
tem, and,  unless  the  dose  is  frequently  repeated,  and  the 
powers  of  nature  worn  out  by  overexcitement,  no  injurious 
consequences  ultimately  result.  Such  is  the  obvious  oper- 
ation of  opium  when  moderately  taken ;  but  other  effects, 
very  important  in  a  remedial  point  of  view,  are  also  ex- 
perienced. All  the  secretions,  with  the  exception  of  that 
from  the  skin,  are  in  general  either  suspended  or  dimin- 
ished ;  the  peristaltic  motion  of  the  bowels  is  lessened ; 
pain  and  inordinate  muscular  contraction,  if  present,  are 


EFFECTS  OF  ALCOHOL    ON  NERVOUS  SYSTEM.      257 

allayed ;  and  general  nervous  irritation  is  composed,  if  not 
entirely  relieved." 

Cocaine.  —  Cocaine  is  an  alkaloid  extract  of  a  shrub 
native  to  the  Andes.  It  is  much  used  by  the  natives  for 
sustenance  during  long  journeys.  It  is  a  cerebral  stimu- 
lant, developing  a  remarkable  power  of  enduring  hunger 
and  fatigue.  Its  effects  are  similar  to  those  of  coffee,  but 
are  more  intense.  Large  doses  have  a  narcotic  effect  and 
cause  hallucinations.  Its  long-continued  use  is  followed 
by  insomnia,  decay  of  moral  and  intellectual  power,  ema- 
ciation, and  death.  Locally,  it  is  a  powerful  anesthetic  in 
a  limited  area  of  surface,  hence  is  valuable  for  minor  sur- 
gical operations. 

Chloral  Hydrate.  —  This  drug  is  frequently,  but  incor- 
rectly, called  chloral.  It  is  a  powerful  hypnotic,  anti- 
spasmodic,  and  depressant  to  the  brain  and  spinal  nerve 
centers,  and,  to  a  limited  extent,  is  an  anesthetic.  It  is 
very  useful  in  fevers  accompanied  by  cerebral  excitement, 
and  in  convulsions.  Its  hypnotic  effects  have  led  to  its 
use  by  individuals  without  a  physician's  prescription,  and 
often  with  fatal  results.  No  drugs  of  this  class  should  be 
used  except  under  the  advice  of  a  physician. 

Chloroform.  —  In  a  similar  way  this  anesthetic,  whose 
discovery  is  one  of  the  greatest  importance  in  modern  sur- 
gery, is  abused  for  the  sake  of  its  effect  on  the  system, 
and  the  hold  such  a  habit  gets  over  the  user  is  similar  to 
that  of  the  alcohol  or  opium  habit. 

The  Use  of  Narcotics.  —  The  use  of  anesthetics  and 
narcotics  may  all  be  said  to  be  typified  by  the  use  of  alco- 
hol. Not  that  they  are  all  stimulants,  though  many  of 
them  are,  in  small  doses,  or  in  the  earlier  stages  of  their 


258  PHYSIOLOGY. 

effects.  They  all  act  on  the  nervous  system.  They  pro- 
duce a  pleasurable  effect  or  they  bring  relief  from  pain. 
The  use  of  many  of  them  is  begun  during  illness,  when 
they  are  administered  to  relieve  pain,  as  in  neuralgia. 
The  habit,  once  formed,  is  hard  to  break.  Others,  having 
heard  of  the  soothing  effects  of  these  drugs,  are  unwise 
enough  to  experiment  on  themselves.  Only  the  confes- 
sions of  such  victims,  and  the  degrading  effects  on  char- 
acter, show  how  powerful  is  the  sway  which  this  class  of 
drugs  gains  over  those  who  yield  to  their  influence.  Let 
no  one  flatter  himself  that  he  has  a  strong  will  and  can 
control  himself.  The  history  of  their  use  is  ever  the 
same.  They  enslave.  They  destroy. 

Tobacco.  —  The  use  of  tobacco  is  needless.  Man  gets 
along  well  enough  without  it.  It  is  injurious  to  many.  It 
is  an  expensive  habit.  Many  a  man  spends  enough  on 
tobacco  to  send  a  boy  through  college.  With  the  excellent 
cheap  printing  of  to-day,  many  of  the  very  best  books  may 
be  bought  for  the  money  that  is  paid  for  as  many  cigars. 
Even  for  those  who  can  abundantly  afford  it,  it  seems  ex- 
tremely selfish,  when  it  is  needless,  and  there  is  so  much 
good  that  might  be  done  with  the  money.  Another  very 
selfish  feature  is  that  so  many  men  do  not  seem  to  con- 
sider the  fact  that  the  air  is  public  property,  and  they 
have  no  right  to  fill  the  air  with  any  gas  or  smoke  that  is 
offensive  to  others.  Very  likely  many  men  derive  great 
comfort  from  the  use  of  tobacco  after  they  have  once 
formed  the  habit,  but  most  of  these  were  made  sick  in 
learning,  showing  that  the  use  is  unnatural. 

Nicotine.  —  The  active  material  in  tobacco  is  a  sub- 
stance called  nicotine.  It  is  a  violent  poison.  A  drop  of 
it  in  concentrated  form  will  kill  a  dog. 


EFFECTS   OF  ALCOHOL    ON  NERVOUS  SYSTEM.     259 

General  Effects  of  Tobacco  on  the  System.  —  Tobacco 
usually  diminishes  the  natural  appetite  for  food  and  inter- 
feres with  digestion.  It  often  affects  the  stomach  and 
induces  a  craving  for  alcoholic  drink.  The  eyes  are  fre- 
quently affected.  Smoking  often  irritates  the  mouth  and 
throat  sufficiently  to  make  the  voice  husky.  The  heart 
also  is  very  frequently  affected,  the  beat  becoming  un- 
steady. The  muscles  are  in  some  cases  weakened  and 
affected  by  trembling. 

Cigarette  Smoking.  —  It  seems  to  be  clearly  proved 
that  cigarette  smoking  is  very  injurious,  especially  to  boys. 
And  if  men  smoke  cigars,  the  example  is  set  for  the  boys 
to  smoke  cigarettes.  Some  of  the  cigarettes  are  said  to 
be  steeped  in  preparations  of  opium,  so  that  the  use  of 
cigarettes  is  often  subjecting  the  user,  not  only  to  the 
tyranny  of  tobacco,  but  that  of  opium  as  well. 

Perhaps  Robinson  Crusoe  might  have  been  excused  for 
using  tobacco,  having  no  one  to  save  money  for,  no  unfor- 
tunates to  aid,  no  children  to  educate,  no  one  to  whom  he 
might  set  a  bad  example,  no  one  whose  breath  of  air  he 
could  contaminate,  no  one  to  smell  his  breath,  no  one  to 
see  the  offensive  results.  But  a  man,  living  in  the  society 
of  so  many  to  whom  this  habit,  in  all  its  features,  is  so 
disgusting  and  in  every  way  offensive,  ought  seriously  to 
consider  whether  he  is  doing  right  in  continuing  such  a 
practice. 

Many  boys  seem  to  think  it  is  manly ;  they  wish,  to  do 
as  others  do.  It  is  not  manly  to  imitate  any  one.  Do 
nothing  simply  because  some  one  else  does  it.  To  do  this 
is  to  be  a  slave,  to  be  led.  And  one  bad  feature  of  the 
tobacco  habit  is  that  one  makes  himself  a  slave  to  the 
weed.  For,  like  other  narcotics,  it  has  a  powerful  in- 


260  PHYSIOLOGY. 

fluence  on  the  system,  and  the  habit,  once  formed,  is  hard 
to  break. 

How  many  men  have  been  heard  to  say,  "  I  wish  I  had 
never  formed  the  habit." 

Has  any  one  in  middle  or  later  life  ever  been  heard  to 
say,  "  I  wish  I  had  formed  this  habit "  ? 

READING.  —  The  Nature  and  Effects  of  Alcohol  and  Nar- 
cotics, Luce  ;  Diseases  of  Inebriety,  Crothers  ;  Inebriety,  its 
Causes,  its  Results,  its  Remedy,  Clum ;  Inebriety,  Palmer. 


Summary. —  i.  The  most  important  physiological  effects  of  alcohol 
are  on  the  nervous  system. 

2.  Many  physicians  regard  inebriety  as  a  disease. 

3.  The  use  of  alcohol  weakens  the  will  power. 

4.  Narcotics  produce  anesthesia,  or  loss  of  feeling. 

5.  Hence  narcotics  are  useful  in  deadening  pain,  but  their  use  is 
dangerous. 

6.  Opium  is  one  of  the  most  widely  used  of  the  narcotics. 

7.  Tobacco  is  needless  and  in  many  cases  harmful. 

8.  Cigarette  smoking  is  very  injurious,  especially  to  the  young. 

Questions.  —  i .   Why  is   cigarette  smoking    more    injurious  than 
cigar  smoking  ? 

2.    How  does  the  opium  habit  often  begin  ? 


CHAPTER   XVII. 

GENERAL  CONSIDERATIONS  CONCERNING  THE  NERVOUS 

SYSTEM. 

Nerve  Stimuli.  —  Natural  nerve  impulses  that  run  out- 
ward are  ordinarily  started  by  the  action  of  some  nerve 
cell  or  cells,  as  from  the  gray  matter  of  the  brain  or  of 
the  spinal  cord. 

Nerve  impulses  coming  inward  may  be  started  in  sev- 
eral ways.  Ordinarily  by  some  one  of  a  few  forces  that 
are  capable  of  affecting  the  nerve  endings.  Mechanical 
force,  as  pressure,  acts  on  the  nerve  endings  of  the  skin, 
and  starts  nerve  impulses  which  are  carried  to  the  brain 
and  rouse  certain  cells  to  activity,  and  give  us  the  sensa- 
tion of  touch.  The  vibrations  known  as  light  excite  the 
special  nerve  endings  in  the  retina,  but  affect  no  other 
nerve  endings.  Sound  is  appreciated  only  by  the  endings 
of  the  auditory  nerve.  Certain  gases  or  fine  particles 
affect  the  olfactory  nerve  endings,  and  certain  substances 
may  give  the  sense  of  taste  by  acting  on  the  ends  of  nerves 
in  the  mouth.  Different  nerves,  then,  are  adapted  to  re- 
ceiving impressions  from  the  action  of  different  forces. 

Kinds  of  Nerve  Stimuli.  —  There  are  four  kinds  of 
nerve  stimuli, — electrical,  mechanical,  thermal,  and  chemi- 
cal. In  experiment,  electricity  is  usually  the  best  stimulus  ; 
mechanical  stimuli,  as  used  in  the  experiments  with  the 
muscle-nerve  preparation  from  the  frog,  by  cutting  or 
pinching  the  nerve,  may  be  employed ;  heat,  as  in  touch- 

261 


262  PHYSIOLOGY. 

ing  the  nerve  with  a  hot  wire,  or  holding  a  hot  wire  near 
the  nerve,  may  be  used  as  a  stimulus ;  chemical  stimuli,  as 
acids,  strong  salt  solution,  etc.,  may  also  be  used. 

Essential  Similarity  of  All  Nerve  Fibers.  —  It  is  to  be 
noted  that  while  special  stimuli  act  on  specially  modified 
nerve  endings,  all  nerve  fibers  are  essentially  alike,  and 
the  nerve  impulse,  however  started,  is  probably  the  same 
kind  of  force.  For  instance,  cutting  the  optic  nerve,  or 
severe  shock,  as  a  blow  on  the  head,  causes  a  sensation  of 
light  not  quite  so  definite,  but  essentially  the  same  as 
though  light  had  acted  on  the  retina,  and  thus  started  the 
nerve  impulse,  instead  of  a  mechanical  stimulus  acting  on 
the  nerve  fibers  between  the  retina  and  the  brain. 

Relation  of  Stimulus  and  Sensation.  —  If  we  apply  a 
stimulus  of  a  given  intensity,  as  of  an  electric  current, 
whose  intensity  can  be  measured,  it  causes  a  sensation  of 
a  certain  degree.  Doubling  the  stimulus,  or  increasing  it 
by  a  definite  amount,  does  not  increase  the  intensity  of  the 
sensation  to  the  same  degree.  The  sensations  do  not 
increase  at  the  same  rate  as  the  stimuli.  To  increase  the 
sensations  arithmetically,  the  stimuli  must  increase  geo- 
metrically. 

Reaction  Time.  —  "  Reaction  time  "  is  the  time  between 
the  application  of  a  stimulus  and  the  signal  given  as  a 
response  to  show  that  the  stimulus  has  been  "felt."  Thus 
a  blindfolded  person  gives  a  signal  as  soon  as  he  is  touched. 
This  interval  between  the  stimulus  and  response  varies 
with  the  individual,  mode  of  stimulation,  health,  attention, 
etc.  It  is  from  one  tenth  to  one  fifth  of  a  second  ;  is  short- 
est for  touch  ;  longer  for  sight  than  for  hearing.  The  total 
reaction  time  is  occupied  by  (i)  the  time  of  conducting 
the  nerve  impulse  to  the  brain,  (2)  the  time  occupied  in 


NERVOUS  SYSTEM  IN  GENERAL. 


263 


the  cerebral  cortex  in  the  perception  of  the  sensation 
and  the  formation  of  the  volition,  (3)  the  time  of  conduct- 
ing the  motor  impulse  and  giving  the  signal.  The  greater 
part  is  in  the  middle  interval,  i.e.  the  central  elaboration, 
during  which  the  entering  impression  gives  rise  to  an  out- 
going impulse. 

Reflex  Action.  —  In  a  previous  diagram  of  reflex  action, 
a  single  cell  was  represented  as  receiving  the  afferent  im- 

Nerve  Cells  connected  by  Interlacing  Nerve  Network 


Afferent  Nerve  Fibe 


Sensory 
Epithelium 


Efferent  Nerve  Fiber 


Muscle 


Fig.  83.     Diagram  of  Reflex  Action. 

pulse  and  sending  out  an  efferent  one.  It  is  more  proba- 
ble that  at  least  two  cells  are  concerned  in  such  an  act,  one 
receiving  the  incoming  impulse,  and  influencing,  by  means 
of  fine  connecting  branches,  a  second  cell  which  sends  out 
the  motor  impulse,  as  shown  in  Fig.  83. 

Connection  of  Brain  Centers.  — We  have_seen  that  the 
brain  functions. are  more  or  less  localized.  We  also  know 
that  the  cortex  receives  impressions  through  the  channels 


264 


PHYSIOLOGY. 


Writing 


Speech 


of  the  different  sense  organs,  and  we  can  respond  through 
various  channels,  —  speech,  writing,  facial  expression,  etc. 
We  would  therefore  expect,  theoretically,  that  the  various 
parts  of  the  cortex  of  the  brain  are  connected.  As  a 

matter  of  fact,  we 
find  anatomically 
that  this  is  the 
case.  Not  only 
are  the  cells  of 
the  gray  mat- 
ter connected 
with  the  various 
parts  of  the  body, 
but  cells  of  differ- 
ent parts  of  the 
cortex  are  in  com- 
munication with 
each  other  by  what 
are  called  "  as- 
sociation fibers." 
Thus  a  sensation 
roused  in  one  part 
of  the  brain  gives 
rise  to  the  sending 
out  of  an  impulse 
from  another  part 
of  the  brain  to 
produce  the  re- 
sponse. 


Fig    84.     Connection  of  Brain  Centers  by  Association 
Fibers.    (After  Landois  and  Stirling.) 

(The  dotted  lines  from  the  hand,  mouth,  and  eye  rep- 
resent afferent  fibers  from  the  skin,  muscles,  and  joints 
of  the  hand,  lips,  orbit,  etc.) 


The  Nature  of  Sensation.  —  Of  the  real  nature  of  sen- 
sation we  know  but  little.  Like  consciousness,  we  call  it 
a  condition  of  the  gray  matter  of  the  cerebral  convolutions. 


NERVOUS  SYSTEM  IN  GENERAL.  26$ 

Perhaps  the  most  practical  definition  of  sensation  that  we 
can  give  is  that  it  is  the  interpretation  that  the  cells  of 
tJie  gray  matter  of  the  brain  give  to  the  nerve  impulses 
that  come  from  without.  This  will  apply  to  ordinary  sen- 
sations. 

Subjective  Sensations.  —  But  sensations  may  be  subjec- 
tive ;  that  is,  they  may  exist  without  any  corresponding 
external  exciting  cause.  For  some  unexplained  reason  the 
cells  of  the  brain  are  active,  and  their  activity,  however 
caused,  constitutes  what  we  call  a  sensation.  Certain 
drugs,  such  as  hashish,  may  excite  an  unusual  degree  of 
cerebral  activity.  Here  the  action  is  roused  through  af- 
ferent nerves,  but  through  unusual  channels ;  that  is,  the 
subject  sees,  but  not  through  the  nerves  of  sight.  Many 
hallucinations  are  explainable  to  a  certain  degree ;'  others 
we  cannot  account  for. 

The  Relative  Nature  of  Sensations.  —  If  one  hand  be 
held  in  a  basin  of  hot  water  and  the  other  in  a  basin  of 
cold  water,  and  then  the  two  be  suddenly  plunged  into 
a  third  basin  containing  tepid  water,  a  sensation  of  cold  will 
be  received  from  the  hand  that  was  in  the  hot  water,  while 
the  hand  from  the  cold  water  will  feel  heat.  Sensations 
depend  on  comparison  and  contrast.  After  listening  to 
low  sounds,  a  sudden  loud  noise  is  painful ;  and  after  hear- 
ing loud  noises,  it  is  difficult  to  detect  slight  sounds.  We 
hardly  notice  the  gradual  fading  of  the  light  at  sunset. 
And  the  nose  does  not  usually  detect  the  slow  fouling  of 
the  air  in  a  room ;  but  let  one  come  in  from  the  fresh  out- 
side air,  and  the  contrast  is  striking.  A  constant  current 
of  electricity  usually  causes  a  muscular  contraction  at  the 
time  the  current  enters  the  muscle  and  at  the  time  when 
the  current  is  stopped,  that  is,  at  the  "  making  "  and  the 


266  PHYSIO  LOG  Y. 

"breaking"  of  the  current;  but  the  muscle  ordinarily  re- 
mains inactive  while  the  current  is  passing. 

Induction  Current  used  in  Physiological  Experiment. — The  in- 
terrupted current,  or  induction  current,  is  therefore  commonly  employed 
as  a  stimulus  in  physiological  experiment.  A  sudden  change  seems 
to  be  requisite  for  producing  the  nerve  impulse  necessary  to  rouse 
a  sensation  in  ordinary  circumstances.  Pressure  may  be  applied  so 
gradually  that  we  fail  to  notice  it.  The  art  of  the  pickpocket,  of  the 
ventriloquist,  of  the  sleight-of-hand  performer,  depends  largely  on  this 
fact.  Attention  is  called  to  something  else,  and  the  work  is  either 
quickly  done  when  attention  is  completely  absorbed  on  something  else, 
or  the  act  is  so  gradual  that  no  sudden  change  is  noted.  In  smelling 
it  is  often  necessary  to  sniff;  the  sudden  rush  of  particles  of  air  bearing 
the  odorous  particles  against  the  surface  bearing  the  nerve  endings 
seems  to  be  necessary. 

Dreams.  —  Dreams,  due  to  more  or  less  perfect  brain  activity,  are 
often  traceable  to  nerve  impulses  brought  from  the  digestive  tract,  from 
the  respiratory  organs,  from  the  skin  (heat  and  cold  and  pressure), 
from  sound,  from  any  internal  organ,  according  to  the  condition  of  the 
blood,  pressure,  etc.  It  seems  to  be  well  settled  that  dreams  seeming 
to  cover  long  periods  of  time  really  take  place  in  a  very  short  space  of 
time,  just  as  sometimes  during  waking  hours  thoughts  fly  through  the 
mind  in  countless  numbers  and  with  incredible  swiftness. 

Ignoring  Nerve  Currents.  —  Do  we  have  dreams  when  we  recall 
none?  Without  attempting  to  answer  this  question  it  is  well  to  note 
that  the  brain  undoubtedly  is  constantly  receiving  nerve  currents  to 
which  it  pays  no  heed,  or  at  least  of  which  we  are  not  conscious. 
For  instance,  our  clothing  is  touching  nearly  the  whole  of  the  surface 
of  our  bodies,  and,  plainly,  the  surfaces  thus  touched  are  affected. 
Undoubtedly  currents  go  to  the  brain,  but  as  they  are  of  no  significance 
in  ordinary  circumstances,  we  learn  to  disregard  them.  If  a  savage 
were  suddenly  clothed  as  fully  as  we  are,  he  would,  for  a  long  time, 
be  continually  conscious  of  the  fact. 

Judgment.  —  In  what  is  called  Aristotle's  experiment, 
the  experimenter  crosses  the  first  and  second  finger,  and 
feels  an  object  with  the  fingers  thus  crossed  and  eyes  shut. 


NERVOUS  SYSTEM  IN  GENERAL.  267 

If  a  marble  be  rolled  about  by  the  two  fingers  thus  crossed, 
it  seems  to  be  two.  Here  we  use  judgment  with  the  sen- 
sation. Ordinarily,  we  could  not  feel,  at  the  same  time, 
one  simple  solid  object  with  the  outside  of  the  first  and  the 
inside  of  the  second  finger.  This  illustrates  how  we  are 
constantly  using  our  judgment  in  interpreting  our  sen- 
sations. We  see  few  things  as  they  are  in  themselves. 
We  see  nearly  everything  in  the  light  of  past  experiences. 

Lingering  Effect  of  Sensations.  — We  have  noted  the  lingering 
effects  of  sensations,  how  sights  and  sounds  linger  and  are  fused  one 
with  the  other.  So  we  get  continuous  light  from  a  series  of  flashes 
if  they  follow  each  other  in  sufficiently  rapid  succession,  and  continu- 
ous sound  from  a  series  of  sounds  that  would  be  heard  separately  if 
they  are  more  than  about  a  sixteenth  of  a  second  apart.  So  with 
touch,  if  the  finger  be  held  against  the  teeth  of  a  revolving  wheel,  if 
the  wheel  revolve  slowly,  the  touch  of  each  tooth  may  be  felt,  but  when 
it  whirls  more  rapidly  the  sensation  becomes  that  of  continuous  pres- 
sure. Experience  and  experiment  both  go  to  show  that  probably 
nothing  is  wholly  forgotten.  Whatever  acts  upon  a  cell  of  nervous 
matter  makes  its  mark.  It  may  become  dim,  but  it  is  never  completely 
obliterated.  The  testimony  of  persons  rescued  from  drowning,  and  other 
similar  experiences,  goes  to  show  that  the  record  was  yet  in  the  mind. 
We  may  fail  to  recollect,  but  we  ever  remember. 

Habits  are  Acquired  Reflex  Actions.  —  The  work  of 
the  spinal  cord  is  that  of  a  subordinate  officer,  whose  duty 
is  to  relieve  his  superior,  the  brain,  of  many  small  tasks, 
and  to  afford  him  relief  from  having  all  the  details  con- 
stantly on  his  mind.  If  we  learn  to  do  many  things  me- 
chanically, we  save  the  effort  of  doing  them  by  conscious 
effort  and  act  of  will.  Whatever  we  do  for  the  first  time 
requires  careful  attention.  To  learn  any  new  muscular 
action,  such  as  a  new  step  in  marching,  fingering  a  musical 
instrument,  or  typewriting,  requires  effort;  they  produce 
more  or  less  fatigue.  Subsequent  effort  in  doing  the  same 


268  PHYSIOLOGY. 

thing  is  very  much  less,  showing  that,  in  many  cases, 
fatigue  is  mental  rather  than  muscular.  What  we  do  from 
habit,  and  cheerfully,  is  easily  done.  Hence  the  desira- 
bility of  forming  good  habits,  that  we  may,  without  un- 
necessary effort,  —  that  is,  without  loss  of  energy,  —  do 
what  is  needed  for  our  well-being. 

Fatigue  from  Standing.  —  We  are  not  conscious  of 
expending  energy  in  standing  until  we  begin  to  be  weary ; 
but  the  fact  that  a  blow  on  the  head  causes  one  to  fall 
reveals  the  fact  that  the  brain  is  constantly  sending  mes- 
sages to  the  muscles  to  make  them  act.  The  shock  of  the 
blow  has  stopped  the  sending  forth  of  these  messages,  and 
so  the  body  is  no  longer  supported.  None  of  the  muscles 
that  support  the  body  have  been  injured  or  even  touched. 

The  Usefulness  of  Resting.  —  We  have,  in  youth,  such 
a  boundless  store  of  energy  that  we  do  not  sufficiently 
consider  these  matters.  But  if  one  wishes  to  follow  the 
intellectual  life  long  and  successfully,  he  must  learn  to 
economize  energy,  and  to  direct  his  forces  into  useful 
channels.  And  one  important  part  of  this  knowledge  is 
learning  how  to  rest.  It  is  an  art  that  very  few  have  well 
learned. 

Nervous  System  compared  to  a  Telegraph  System.  - 

The  brain  is  like  a  telegraph  office  in  both  receiving  and 
sending  out  messages.  Unlike  the  telegraph  office,  it  has 
one  set  of  fibers  to  bring  currents  in  (afferent),  and  another 
to  carry  currents  outward  (efferent). 

Efferent  Currents.  —  We  have  concerned  ourselves  thus 
far  chiefly  with  efferent  nerve  fibers  and  efferent  currents. 
These  efferent  currents  are  sent  mainly  to  muscles,  to 
make  them  shorten  or  to  relax,  or  to  gland  cells,  to  control 


NERVOUS  SYSTEM  IN  GENERAL.  269 

their  activity.  The  only  other  efferent  currents,  so  far 
as  known,  are  those  which  possibly  go  to  the  cells  of 
the  tissues  to  regulate  their  nutrition  or  their  heat  pro- 
duction. 

Having  given  so  much  attention  to  the  outgo  of  nerve 
impulses,  let  us  ask  the  question,  "  What  about  the  in- 
coming nerve  currents  ? " 

Afferent  Currents.  —  "  All  life  long  the  never-ceasing 
changes  of  the  external  world  continually  break  as  waves 
on  the  peripheral  endings  of  the  afferent  nerves ;  all  life 
long  nervous  impulses,  now  more,  now  fewer,  are  continu- 
ally sweeping  inward  toward  the  center;  and  the  nervous 
metabolism,  which  is  the  basis  of  nervous  action,  must  be 
at  least  as  largely  dependent  on  these  influences  from 
without  as  on  the  mere  chemical  supply  furnished  by  the 
blood.  We  must  regard  the  supereminent  activity  of  the 
cortex  and  the  characters  of  the  processes  taking  place  in 
it  as  due  not  so  much  to  the  intrinsic  chemical  nature  of 
the  nervous  substance,  which  is  built  up  into  the  cortical 
gray  matter,  as  to  the  fact  that  impulses  are  continually 
streaming  into  it  from  all  parts  of  the  body ;  that  almost 
all  influences  brought  to  bear  on  the  body  make  themselves 
felt  by  it.  To  put  the  matter  in  a  bald  way  we  may  ask 
the  question,  What  would  happen  in  the  cortex  if,  its  or- 
dinary nutritive  supply  remaining  as  before,  it  were  cut 
adrift  from  afferent  impulses  of  all  kinds  ?  We  can  hardly 
doubt  but  that  volitional  and  other  psychical  processes 
would  soon  come  to  a  standstill,  and  consciousness  vanish. 
This  is,  indeed,  roughly  indicated  by  the  remarkable  case 
of  a  patient  whose  almost  only  communication  with  the 
external  world  was  by  means  of  one  eye,  he  being  blind  in 
the  other  eye,  deaf  of  both  ears,  and  suffering  from  gen- 


270  PHYSIOLOGY. 

eral  anesthesia.     Whenever  the  sound  eye  was  closed  he 
went  to  sleep."   -FOSTER. 

Let  us  turn  from  the  consideration  of  outgoing,  or 
efferent,  nerve  impulses  and  their  resulting  action  to  the 
incoming,  or  afferent,  nerve  impulses  and  the  activity 
which  they  rouse  in  the  gray  matter  of  the  cerebrum  — 
sensation. 

READING.  —  Wear  and  Tear,  Mitchell ;  Power  through 
Repose,  Call ;  Technique  of  Rest,  Brackett. 


Summary.  —  i.    Nerves  may  be  stimulated  by  mechanical  force, 
chemical  action,  heat,  and  electricity. 

2.  Electricity  is  the  most  convenient  nerve  stimulus  for  physiological 
experiment.     The  induction  current  is  usually  employed. 

3.  To  increase  sensations  arithmetically  stimuli  must  increase  geo- 
metrically. 

4.  Reaction  time  is  the  interval  between  the  application  of  a  stimu- 
lus and  the  response. 

5.  Sensations  are  relative. 

6.  Habits  are  acquired  reflex  actions. 

7.  The  nervous  system  is  unlike  the  telegraph  system  in  using  one 
set  of  fibers  for  receiving  and  another  for  sending  messages. 

Questions.  —  i.    Is  the  difference  in  "reaction  time11  in  individuals 
of  any  significance  ? 

2.    Why  are  slight  wounds  in  a  battle  often  unperceived  ? 


CHAPTER   XVIII. 
THE   GENERAL   SENSES. 

The  Body  a  Collection  of  Organs.  —  We  have  been 
considering  the  body  as  a  collection  of  organs  working 
together  to  serve  the  brain,  the  mechanism  through  which 
the  mind  operates. 

We  have  especially  studied  the  muscles  as  the  only 
means  by  which  the  mind  manifests  itself  to  the  outer 
world. 

Influences  from  the  External  World.  —  But  how  much 
mind  would  we  have  if  we  did  not  receive  something  from 
the  outer  world  ?  Read  the  story  of  Kaspar  Hauser.  We 
are  continually  getting  knowledge  of  the  outer  world  and 
of  the  condition  of  our  own  bodies  through  the  afferent 
nerves.  We  may  never  know  fully  what  consciousness  and 
thought  are,  but  we  can  understand  that  to  the  brain  are 
continually  streaming  nerve  impulses  that  convey  messages 
which  the  brain  more  or  less  completely  interprets. 

Classification  of  the  Senses.  —  These  incoming  currents 
pass  along  myriads  of  nerve  fibers.  But  the  nerve  fibers 
are  all  essentially  alike.  And  the  kinds  of  sensations  that 
these  currents  arouse  in  the  brain  are  but  few.  It  is  diffi- 
cult to  classify  the  senses,  but  it  will  serve  our  convenience 
to  divide  them  into  two  groups. 

General  Sensations  and  Special  Senses.  —  In  distinc- 
tion from  the  special  senses,  sight,  hearing,  etc.,  are  the 

271 


2/2  PHYSIOLOGY. 

general  sensations  already  referred  to,  such  as  hunger, 
thirst,  fatigue,  nausea,  satiety,  faintness,  etc.  They  are 
often  called  "common  sensations,"  and  Martin  designates 
them  as  "  sensations  which  we  do  not  mentally  attribute  to 
the  properties  of  external  objects,  but  to  the  conditions  of 
our  own  bodies." 

General  Sensations.  —  Nerve  endings  in  different  parts 
of  the  body  may  be  affected  by  the  blood  and  the  lymph, 
and  give  us  sensations  of  comfort,  discomfort,  restlessness, 
fatigue,  faintness,  etc.  These  are  called  general  sensa- 
tions. They  are  probably  due  to  the  condition  of  the 
blood,  or  to  the  condition  of  nutrition  of  the  various  parts 
of  the  body.  Thus  after  muscular  exercise  the  muscles  are 
acid  in  their  reaction,  while  they  are  alkaline  after  resting ; 
after  exercise  carbon  dioxid  accumulates  in  them  to  a  cer- 
tain extent.  Hunger  and  thirst  come  on  after  abstinence 
from  food  and  drink,  or  after  work  exhausting  the  tissues. 
The  presence  of  the  various  waste  products,  or  the  condi- 
tion of  the  cells  as  the  result  of  their  activity,  acting 
through  the  nerve  endings  in  the  tissues,  keep  the  nerve 
centers  informed  as  to  the  condition  of  the  parts  of  the  body. 
If  these  conditions  are  extreme,  we  may  have  definable  sen- 
sations, but  ordinarily  the  sensations  are  of  an  undefinable 
sort  which  we  designate  as  "  general  sensations." 

The  Muscular  Sense.  —  As  an  example,  we  will  take 
the  case  of  estimating  the  weight  of  an  object  by  holding 
it  in  the  hand.  Our  estimate  is  thought  by  some  to  be  the 
result  of  (i)  direct  consciousness  of  the  degree  of  effort 
put  forth  ;  but  probably  it  is  (2)  a  sensation,  or  complex  of 
sensations,  aroused  by  nerve  impulses  from  the  organs 
used.  There  are  afferent  nerve  fibers  with  endings  in 
(i)  the  skin,  (2)  the  muscles  and  tendons,  (3)  the  joints, 


THE  GENERAL  SENSES.  2/3 

In  extending  the  arm  and  moving  it  up  and  down,  all  three 
of  these  sets  of  nerve  endings  are  probably  stimulated,  and 
impulses  thence  conveyed  to  the  brain. 

Muscular  Sense  and  General  Sensibility.  —  It  is  a 
matter  of  doubt,  whether  or  not  the  impulses  from  the 
muscles  are  predominant,  and  consequently  whether  the 
term  "  muscular  sense  "  is  the  most  appropriate.  Peculiar 
nerve  endings  have  been  found  in  the  tendons,  and  the 
joints  are  believed  to  have  an  especially  rich  nerve  supply. 
It  is  not  necessary  that  we  actively  use  the  muscles  to  have 
sensations  of  this  kind.  In  passive  moments,  as  the  rais- 
ing of  the  arm  by  another  person,  we  have  a  "  sense  of 
position"  of  the  parts,  a  considerable  share  of  which  is 
probably  due  to  the  tension  of  the  skin  and  changes  in  the 
joints.  There  is,  of  course,  some  tension  of  the  muscle, 
even  in  this  passive  movement,  that  might  affect  nerve 
endings  in  it.  The  muscular  sense  is  closely  related  to  the 
general  sensibility  already  mentioned,  if  not  a  modified 
form  of  it. 

Importance  of  Muscular  Sense.  —  It  is  difficult  to  real- 
ize the  importance  of  this  sense  in  our  daily  experience. 
We  probably  underestimate  it,  and  attribute  to  sight  too 
much  of  our  knowledge  of  the  external  world.  The  funda- 
mental facts  concerning  the  objects  about  us  are  not  ob- 
tained through  sight  alone.  Such  knowledge  is  based  on 
complex  judgments  concerning  the  meaning  of  auditory 
and  visual  phenomena,  according  as  they  have,  in  past  ex- 
perience, been  interpreted  by  tactile  and  muscular  percep- 
tions. That  is,  when  reduced  to  its  simplest  terms  our 
most  practical  and  important  knowledge  of  the  world  is 
the  outgrowth  of  tactile  and  muscular  perceptions ;  by  and 


2/4  PHYSIOLOGY. 

with  them  all  other  sense  perceptions  have  been  corrected 
and  compared. 

Dependence  of  Sight  on  Muscular  Sense  and  Touch. — 
An  illustration  of  the  assistance  which  touch  and  the  mus- 
cular sense  give  to  the  sense  of  sight  is  furnished  in  the 
case  of  a  boy  who  had  been  blind  from  birth,  and  received 
sight  at  the  age  of  twelve  years  by  means  of  a  surgical 
operation.  At  first  he  could  not  distinguish  a  globe  from 
a  circular  card  of  the  same  color  until  he  had  touched  them. 
He  knew  the  peculiar  features  of  the  dog  and  the  cat  by 
feeling,  but  not  by  sight.  Happening  one  day  to  pick  up 
the  cat  he  recognized  for  the  first  time  the  connection  be- 
tween the  new  sense  of  sight  and  the  old  familiar  ones  of 
touch  and  the  muscular  sense.  On  putting  the  cat  down 
he  said,  "So,  puss,  I  shall  know  you  next  time." 

Pain.  —  When  a  heavy  weight  is  laid  on  the  hand  it  may 
cause  pain.  It  would  at  first  seem  that  the  ordinary  pres- 
sure sense,  when  unduly  exaggerated,  becomes  pain.  But 
there  seem  good  reasons  for  considering  pain  as  a  distinct 
sense  from  that  of  touch  intensified.  It  is  thought  that 
there  are,  throughout  all  parts  of  the  body,  nerves  of  "com- 
mon sensibility  "  or  "  general  sensibility,"  which  keep  the 
nerve  centers  informed  as  to  the  condition  of  all  the  various 
tissues,  and  that  ordinarily  we  have  no  sensation  resulting 
from  the  impulses ;  to  use  the  language  of  the  psycholo- 
gist, "  they  do  not  rise  above  the  threshold  of  conscious- 
ness." They  may  have  some  influence  in  adjusting  the 
action  of  the  different  parts.  We  have  seen  how  the  blood- 
flow  to  any  part  is  continually  adjusted  without  our  know- 
ing anything  about  it.  But  we  are  usually  more  or  less 
conscious  of  the  general  condition  of  the  body.  We  call 
by  the  name  of  "  common  sensations "  such  feelings  as 


THE   GENERAL  SENSES.  275 

hunger,  thirst,  nausea,  fatigue,  depression,  melancholy, 
restlessness,  such  as  many  experience  preceding  a  thun- 
derstorm, the  feeling  of  general  discomfort  known  as 
malaise,  and  its  opposite,  the  feeling  of  general  well  being. 
The  body  seems  to  have  a  set  of  nerves  to  give  information 
as  to  the  state  of  nutrition  of  the  body,  and  as  to  its  condi- 
tion generally.  These  nerves,  when  the  system  is  dis- 
ordered in  any  part,  may  bring  messages  that  cause  intense 
pain.  Of  course,  they  are  warnings  (they  are  more  than 
mere  warnings  ;  probably  if  the  earlier  indications  of  simple 
discomfort  had  been  heeded  the  later  more  emphatic  mes- 
sages of  pain  would  not  have  been  necessary).  These  mes- 
sages of  pain  demand  attention. 

The  Extent  of  Pain.  —  In  reference  to  pain  in  the  skin, 
it  is  held  that  the  skin,  too,  has  its  nerves  of  general  sensi- 
bility, and  that  these  are  distinct  from  those  of  touch  and 
temperature  sense.  That  when  they  are  unduly  stimulated 
they  give  rise  to  painful  sensations.  It  is  to  be  noted  that 
the  internal  organs  are  ordinarily  devoid  of  feeling,  and 
that  the  skin  is  especially  sensitive.  The  skin  senses  stand 
guard  at  the  outposts,  so  to  speak,  of  the  body's  camp,  and 
give  warning  of  approaching  danger.  No  enemy  may 
enter  without  being  discovered  by  these  keen  sentinels, 
and  the  alarm  is  given.  If  it  is  not  heeded,  great  harm 
may  follow.  And  it  is  a  comfort  to  know  that  the  more 
severe  wounds  do  not  cause  pain  in  proportion  to  their 
extent.  When  a  person  says  his  "  lungs  are  sore "  the 
pain  is  usually  in  the  muscles  of  the  chest  from  coughing. 
While  there  may  be  acute  pain  from  the  lungs,  as  in  pleu- 
risy, there  is  often  deep-seated  lung  disease  without  pain 
from  the  lungs  themselves.  The  muscles  of  the  chest  and 
back  may  be  strained  by  lifting,  and  the  soreness  is  erro- 


2/6  PHYSIOLOGY. 

neously  attributed  to  the  lungs  or  kidneys.  Hence  there 
is  frequently  a  wholly  needless  apprehension  of  deep- 
seated  disorder,  whereas  in  reality  there  is  merely  a  strain 
of  superficial  muscles.  In  amputating  a  limb  the  chief 
pain  is  in  cutting  through  the  skin.  Some  excellent 
authorities  still  hold  the  view  that  pain  is  merely  the 
result  of  intensifying  any  of  the  simple  sensations ;  but  it 
is  generally  held  that  it  results  from  the  excessive  stimula- 
tion of  the  nerves  of  general  sensibility  ;  as  Foster  puts  it, 
"  the  constantly  smouldering  embers  of  common  sensibility 
may  be  at  any  moment  fanned  into  the  flame  of  pain." 

Pain  a  General  Sense.  —  In  the  real  "special  senses," 
—  sight,  hearing,  smell,  taste,  touch,  and  temperature  sense, 
—  we  refer  the  sensation  to  some  external  object,  whereas 
general  sensations  are  subjective,  referred  to  our  bodies. 
Ordinarily  we  do  not  localize  the  common  sensations,  and 
a  further  indication  of  the  relationship  of  pain  and  general 
sensation  is  in  the  lack  of  complete  localization  of  pain. 
Slight  pain,  especially  in  the  skin,  may  be  closely  located, 
but  severe  pain  tends  to  become  indefinite  and  diffuse. 
So  we  may  class  both  the  muscular  sense  and  pain  with 
the  "general"  rather  than  with  the  "special"  senses. 

Hunger  and  Thirst.  —  The  cause  of  these  sensations  in 
a  healthy  body  is  plainly  the  need  of  food  and  water 
throughout  the  system  generally.  The  sensation  of  thirst 
manifests  itself  in  the  throat,  and  the  longing  may  be  tem- 
porarily relieved  by  merely  moistening  the  throat.  So 
hunger  may,  for  the  time,  be  appeased  by  filling  the  stom- 
ach with  indigestible  material.  But  the  sensation  soon 
returns.  The  system  has  a  crying  need,  and  it  is  not  to  be 
put  off  by  any  such  frauds.  That  these  sensations  are 
really  demands  made  by  the  body  as  a  whole  may  be 


THE  GENERAL  SENSES.  277 

shown  by  the  fact  that  they  are  permanently  relieved  by 
introducing  food  and  water  into  the  body  (by  the  rectum, 
for  instance),  in  which  case  the  throat  and  stomach  have 
nothing  given  them  directly.  Since,  however,  food  and 
drink  naturally  enter  by  the  throat  and  stomach,  the 
mucous  membrane  of  these  organs  has  become  spokes- 
man of  the  body  for  its  demands. 

READING. — Pain,  Corning. 


Summary.  —  i .  Brain  action  depends,  in  the  long  run,  upon  im- 
pulses from  without.  If  we  had  no  impressions,  we  could  have  no 
expressions. 

2.  General  sensations  are  referred  to  our  bodies  and  their  condition  ; 
special  sensations  are  regarded  as  attributes  of  external  objects. 

3.  The   "muscular  sense11  probably  depends  chiefly  on  impulses 
from  the  tendons  and  joints. 

4.  The   muscular  sense  is  necessary  for  the  full  interpretation  of 
sight.     It  enables  us  to  judge  of  the  degree  of  effort  put  forth  or  force 
resisted. 

5.  Pain  is  a  general  sensation.    It  is  a  warning — the  cry  of  a  senti- 
nel that  an  enemy  has  passed  the  picket  line. 

6.  Hunger  and  thirst  indicate  the  need  of  food  and  drink.    They  are 
local  signals  of  a  general  want. 

Questions.  —  i.  If  we  had  no  sense  of  pain,  what  might  result? 
2.    If  we  pass  by  a  meal  time  without  eating,  why  does  the  sense  of 
hunger  disappear? 


CHAPTER    XIX. 

THE   SPECIAL  SENSES -TOUCH  AND  TEMPERATURE 

SENSE. 

What  we  learn  by  touching  Objects.  —  Let  one  person 
rest  the  hand  flat  on  the  table,  palm  upward,  and  close  the 
eyes.  An  object  placed  on  the  palm,  by  another  person, 
may  give  rise  to  various  sensations,  so  that  it  may  be 
described  as  rough  or  smooth,  light  or  heavy,  hot  or  cold, 
wet  or  dry,  etc.  If  the  object  is  very  heavy  or  very  hot,  it 
may  cause  pain.  If  now  the  thumb  and  fingers  are  raised 
and  applied  to  the  object,  more  definite  information  will  be 
gained  as  to  its  shape,  size,  surface,  etc.  Now  raise  the 
object  in  the  hand,  and  further  appreciation  will  be  gained 
as  to  its  weight. 

These  experiments  show  that  several  sensations  are  in- 
volved in  the  handling  of  objects,  and  that  the  knowledge 
so  gained  is  complex. 

Cutaneous  Sensations.  —  The  sensations  from  the  ob- 
jects resting  on  the  skin  of  the  passive  hand  may,  proba- 
bly, all  be  referred  to  impressions  made  on  nerve  endings 
in  the  skin,  and  are  called  cutaneous  sensations.  They 
include:  (i)  the  pressure  sense,  or  touch  proper,  (2)  the 
temperature  sense,  and  (3)  pain. 

Nerve  Endings  in  the  Skin.  —  The  skin  consists  of 
two  layers,  the  epidermis  and  the  dermis.  We  need  now 
to  recall  those  conical  elevations  of  the  dermis  that  we  caU 

278 


THE  SENSE  OF  TOUCH. 


279 


papillae.  In  these  papillae  are  certain  important  nerve 
endings.  There  are  several  kinds  of  nerve  endings  in  the 
skin  and  underneath  it  that  receive  the  impressions  which, 
carried  to  the  brain,  give  us  sensations  of  touch  (and  allied 
sensations  to  be  considered  soon).  Pressure  on  the  skin 
affects  these  nerve  endings,  and 
starts  impulses  that  pass  along  the 
sensor  fibers  to  some  nerve  center, 
probably  in  the  spinal  cord,  spinal 
bulb,  or  brain. 


Nerve 

Fig.  85.     Papilla  of  Skin  with 
Touch  Corpuscle. 


Touch  Corpuscles. — These 
"touch  corpuscles"  are  not  re- 
garded as  essential  for  producing 
the  sensation  of  touch,  but  some 
nerve  endings  in  the  skin  do  seem 
necessary ;  for  if  a  nerve  fiber  be 
touched,  not  at  the  end,  but  some- 
where along  its  course,  we  get,  not 

a  sensation  of  touch,  but  a  sensation  of  pain.  Except  in 
the  mouth  and  nose,  we  get  little,  if  any,  sense  of  touch 
from  any  organ  but  the  skin.  The  lining  of  the  digestive 
tube  and  the  internal  organs  generally  are  devoid  of  this 
sense. 

The  Sense  of  Touch.  —  Of  the  special  senses  the  most 
general  is  that  of  touch.  Seeing  and  hearing,  taste  and 
smell,  belong  to  very  limited  parts  of  the  outside  of  the 
body,  but  we  have  the  power  of  feeling  all  over  the  surface 
of  the  body. 

Touch  the  most  General  of  the  Special  Senses.  — 

Not  only  is  the  sense  of  touch  the  most  general  in  being 
distributed  over  the  whole  of  the  body,  but  it  is  the  most 
widely  distributed  sense  throughout  the  animal  kingdom. 


280  PHYSIOLOG  } . 

As  we  descend  the  animal  scale  we  find  many  of  the  lower 
animals  lacking  some  of  the  senses  that  we  possess.  In 
many  of  the  simpler  forms  of  animal  life  there  is  no  evi- 
dence of  a  sense  of  hearing,  and  it  is  extremely  likely  that 
if  they  have  taste  and  smell,  these  senses  are  in  a  very 
rudimentary  state  of  development.  But  in  all  these  forms 
it  is  believed  that  "  feeling  "  exists.  Contact  of  their  exte- 
rior with  foreign  objects  is  so  often  immediately  followed 
by  action  that  little  doubt  remains  about  their  having  the 
sense  of  touch.  Even  ameba  may  have,  in  a  rudimentary 
state,  the  power  to  distinguish  light,  to  taste,  and  to  hear. 
Still  we  have  little  or  no  evidence  on  these  points,  while 
we  are  pretty  sure  that  it  feels. 

The  Pressure  Sense.  —  The  sense  of  touch,  proper,  is 
strictly  a  pressure  sense.  If  we  test  the  skin  to  find  what 
regions  are  able  to  detect  the  least  pressure,  it  is  found 
that  the  forehead  is  most  sensitive,  and  nearly  equally  so 
are  the  temples,  back  of  the  hand,  and  forearm. 

Ability   to    detect    Differences    of    Pressure.  —  The 

ability  to  detect  differences  of  pressure  is  tested  by  finding 
what  is  the  least  addition  to  a  weight  required  to  make  it 
seem  heavier.  For  instance,  if  a  weight  of  1 1  grains  is 
just  perceptibly  heavier  than  one  of  10  grains,  it  does  not 
follow  that  i  grain  added  to  a  weight  of  100  grains  will 
give  any  palpable  increase.  To  100  grains  must  be  added 
10  grains  before  additional  pressure  is  felt ;  that  is,  what- 
ever the  weight,  there  must  be  the  same  ratio  of  increase 
to  increase  the  sensation.  This  is  part  of  the  law,  already 
stated,  of  the  relation  of  stimulus  and  sensation.  The  law 
is  true  only  in  a  general  way  and  will  not  apply  in  extreme 
cases.  It  is  stated  that  the  forehead,  the  lips,  and  temples 
appreciate  an  increase  of  one  fortieth  to  one  thirtieth  of  the 


THE  SENSE  OF  TOUCH.  28 1 

weight  estimated,  while  the  skin  of  the  head,  the  fingers, 
and  the  forearm  require  an  increase  of  one  twentieth  to 
one  tenth  for  its  perception. 

After-Pressure.  —  The  lingering  effect  of  pressure,  or 
after-pressure,  may  be  noticed  after  taking  off  a  tight  hat, 
skate  strap,  shoe,  or  glove. 

Local  Sign.  —  "  If  a  point  of  the  skin  is  touched,  certain 
tactile  corpuscles  are  irritated;  these,  in  turn,  set  up  im- 
pulses in  sensory  nerve  fibers,  and  these  impulses  are  car- 
ried by  the  fibers,  first  to  the  spinal  cord,  and  then  to  the 
brain,  where  the  fibers  end  in  ganglionic  masses  in  the 
gray  matter  of  the  cerebral  cortex.  There  are  thus  pro- 
jected, as  it  were,  on  the  cortex  of  the  brain,  tactile  centers 
for  the  hind  leg,  fore  leg,  neck,  eye,  ear,  trunk,  etc. ;  and 
it  follows  that  each  point  of  the  skin  has  a  corresponding 
point  in  the  cerebral  cortex.  Thus  for  each  stimulation  of 
a  point  of  the  cerebral  cortex  there  is  a  local  sign,  and  so 
we  localize  tactile  impressions." 

Accuracy  in  locating  Touch  Sensations.  —  The  accu- 
racy varies,  and  is  ordinarily  keenest  where  the  nerves  are 
most  numerous.  Where  the  sense  of  locality  seems  to  be 
improved  by  cultivation,  this  appears  to  be  due  to  keener 
discrimination  in  the  brain  cells,  and  not  to  changes  in  the 
nerves  or  nerve  endings.  This  is  indicated  in  the  fact  that 
if  the  fingers  of  one  hand  become  more  discriminating  by 
practice,  it  will  be  found  that  the  fingers  of  the  other  hand, 
without  special  training,  are  also  improved. 

Test  by  Compass  Points. — The  delicacy  of  localizing 
touch  is  usually  tested  in  this  way.  The  blunted  points  of 
a  light  pair  of  compasses  are  allowed  to  rest  gently  on  the 
skin  of  various  parts  of  the  body.  If  the  two  points  are 


282  PHYSIOLOGY. 

very  close  together,  they  will  be/?//  as  one  pressure.  That 
part  which  can  best  distinguish,  as  two  points  of  touch, 
these  blunt  points,  is  considered  the  most  sensitive.  By 
this  test  the  tip  of  the  tongue  is  the  most  sensitive,  being 
able  to  distinguish,  as  two  separate  points  of  contact,  the 
tips  of  the  compasses  when  only  one  twenty-fifth  part  of 
an  inch  apart.  Following  is  the  order  of  degrees  of  sen- 
sitiveness :  tip  of  tongue,  tips  of  fingers,  lip,  tip  of  nose, 
eyelid,  cheek,  forehead,  knee,  neck;  while  the  middle  of 
the  back  seems  least  sensitive,  the  two  points  not  produc- 
ing two  distinct  sensations  until  they  are  more  than  two 
and  a  half  inches  apart.  In  general  those  parts  which  are 
most  used,  and  those  parts  which  are  more  freely  movable, 
are  most  sensitive  ;  for  instance,  the  knee  is  much  more 
sensitive  than  the  middle  of  the  thigh  or  the  middle  of  the 
leg,  and  the  elbow  than  the  middle  of  the  arm  or  forearm. 
If  the  compass  points,  about  half  an  inch  apart,  be  passed 
from  the  palm  to  the  tips  of  the  fingers,  it  will  at  first  seem 
one  line  gradually  separating  into  two  diverging  ones, 
owing  to  the  keener  localizing  power  as  the  finger  tips  are 
approached.  . 

Reference  of  Sensation  to  the  Region  of  Nerve  End- 
ings.—  If  the  " funny  bone,"  or  "crazy  bone,"  be  hit,  i.e. 
if  the  ulnar  nerve  be  bruised  against  the  bone,  sharp  pain 
may  be  felt  in  the  wrist  and  hand,  and  soreness  of  these 
parts  may  be  felt  for  days,  though  they  are  not  in  the 
least  injured,  but  only  the  nerve  at  the  elbow.  The  cur- 
rents along  this  nerve  rouse  sensation  that  we  have  learned 
to  localize  at  the  endings  of  the  nerve  fibers.  So,  too, 
after  amputation  of  a  hand  or  foot,  there  may  for  years 
be  sensations  referred  to  the  missing  member,  probably 
due  to  irritation  of  the  nerves  of  the  stump.  There  is, 


THE  TEMPERATURE  SENSE.  283 

then,  no    certainty  of   getting    rid    of   a   corn    by   ampu- 
tating a  toe.  • 

The  Temperature  Sense.  —  Many  cases  are  on  record 
in  which,  from  accident  or  disease,  the  pressure  sense  was 
lost  and  the  temperature  sense  retained,  or  vice  versa. 
Such  facts  have  led  to  the  belief  that  the  temperature 
sense  is  distinct  from  that  of  touch,  and  has  its  own  nerve 
fibers  and  nerve  endings. 

Two  Sets  of  Nerve  Fibers  for  Distinguishing  Heat  and 
Cold.  —  Since  heat  and  cold  are  only  differences  in  the 
degree  of  heat,  we  would  expect  both  of  these  kinds  of 
impressions  to  be  received  through  one  set  of  nerves. 
There  seems,  however,  to  be  good  evidence  of  two  sets  of 
nerve  fibers,  one  for  heat  and  the  other  for  cold.  In  the  com- 
mon experience  of  the  foot  " going  to  sleep"  by  pressure 
on  the  sciatic  nerve,  or  the  arm  from  compression  of  the 
brachial  nerve,  the  skin  may  be  found,  at  a  certain  stage, 
to  be  only  slightly  sensitive  to  warmth,  while  distinctly 
sensitive  to  cold.  In  some  diseases  of  the  spinal  cord  the 
skin  may  be  affected  by  warmth,  but  not  by  cold.  The 
sensations  of  cold  and  pressure  seem  to  be  usually  lost 
or  retained  together,  while  those  of  warmth  and  pain 
have  a  similar  connection.  But  more  accurate  results  are 
obtained  by  touching  the  skin  with  a  blunt  metal  pencil, 
warmed  or  cooled. 

Warm  Spots  and  Cold  Spots.  —  If  this  be  applied  at 
regular  close  intervals,  it  is  found  that  some  places  feel  the 
warm  point,  while  others  feel  the  cold.  In  this  way  the 
skin  has  been  mapped  out  into  "warm  spots"  (warmth- 
perceiving  spots)  and  "cold  spots"  (cold-perceiving  spots), 
and  still  other  areas  seem  not  sensitive  to  temperature. 


284  PHYSIOLOGY. 

Heat  or  cold,  if  applied  directly  to  a  nerve  trunk,  does  not 
rouse  sensations  of  temperature,  but,  if  strong  enough, 
produces  pain.  If  the  elbow  be  dipped  into  water  at  the 
freezing  point,  a  sensation  not  of  cold  but  of  pain  is  caused, 
and  is  felt  in  the  hand.  Heat  and  cold  are  not  felt  in  the 
digestive  tube  except  at  or  near  the  openings.  If  very  hot 
liquid  be  swallowed,  it  may  cause  pain  in  the  gullet  and 
stomach.  If  a  considerable  quantity  of  warm  liquid  be 
taken,  it  may  give  a  feeling  of  warmth  from  its  effect  on 
the  skin  of  the  abdomen,  by  conduction  of  heat  outward. 
As  with  other  senses,  a  sudden  change  in  the  degree  of 
the  stimulus  is  more  certain  to  rouse  sensation  than  a 
gradual  change. 

READING.  —  The  Five  Senses  of  Man,  Bernstein. 


*   Summary.  —  i.   The  cutaneous  sensations  are  touch  proper,  tem- 
perature sense,  and  pain. 

2.  There  are  touch  corpuscles  in  the  papillae  of  the  dermis. 

3.  Touch  is  the  most  general  of  the  senses,  both  in  its  extent  in  our 
bodies,  and  in  the  number  of  animals  possessing  it. 

4.  Touch  proper,  or  pressure  sense,  is  tested  by  discrimination  of 
additional  pressure. 

5.  Touch  localization  is  tested  by  discrimination  as  to  the  distance 
of  two  points  of  contact. 

6.  Temperature  is  discerned  by  a  special  set  of  nerve  fibers. 

7.  Touch  and  muscular  sense  are  necessary  adjuncts  of  sight  to  give 
correct  perceptions  of  size  and  form. 

Questions.  —  i .  What  is  the  explanation  of  tickling  ? 

2.  Where  does  the  change  occur  by  which  we  become  more  dis- 
criminating in  the  sense  of  touch  ? 

3.  Why  does  an  emotion,  such  as  shame,  make  one  feel  hot  ? 


CHAPTER   XX. 
THE   SENSE  OF  SIGHT. 

The  Sense  of  Sight.  —  In  the  fable  of  the  blind  man 
carrying  the  lame  man  whose  eyes  were  good,  we  have  an 
illustration  of  the  dependence  of  the  various  organs  on 
each  other.  We  have  considered  how  all  our  knowledge, 
both  of  the  condition  of  our  bodies  and  of  the  external 
world,  comes  through  the  nervous  system.  Now,  so  far 
as  the  senses  we  have  studied  are  concerned,  we  learn 
almost  nothing  of  the  external  world  except  from  actual 
contact.  But  sight  reveals  objects  at  a  distance.  With- 
out the  eye  the  body  is  comparatively  helpless.  The  lame 
man  that  the  body  carries  is  a  slight  burden  in  comparison 
with  the  assistance  which  he  renders.  We  can  well  afford 
to  carry  with  us  all  the  time  two  of  these  lame  men  to 
keep  posted  as  to  the  objects  beyond  our  reach.  Of  course 
touch  is  a  great  aid  to  our  interpretations  of  what  we  see. 
But  sight  is  evidently  the  main  avenue  of  knowledge,  the 
royal  road  along  which  come  the  messages  which  bring  us 
the  most  news,  which  give  us  the  keenest  delight ;  which 
makes  us  aware  of  most  that  we  know  of  this  world,  and 
the  only  means  of  knowing  that  there  are  other  worlds 
than  the  one  we  inhabit. 

Protection  of  the  Eye.  —  The  eye  is  set  well  back  in 
its  socket  and  guarded  by  three  projecting  bony  promi- 
nences, —  the  brow,  cheek  bone,  and  the  bridge  of  the  nose. 
It  is  further  protected  by  the  eyelids  and  eyelashes. 

285 


286  PHYSIOLOGY. 

The  Lacrymal  Secretion.  —  The  lacrymal  gland,  or 
tear  gland,  is  just  above  the  outer  angle  of  the  eye,  and 
pours  its  secretion  over  the  eyeball  in  weeping,  or  when 
there  is  need  of  an  unusual  supply  of  tears.  The  lids 
serve  as  curtains  to  admit  or  shut  out  light,  and,  by  wink- 
ing, wash  the  eye  with  their  own  secretion,  a  fluid  mixture 
of  salt  water  and  mucus.  It  is  as  though  a  man  were 
kept  all  the  time  in  front  of  a  plate-glass  window,  with 
water  and  rubber  scraper,  to  keep  it  clean  and  bright. 
The  lacrymal  secretion  is,  ordinarily,  carried  off  as  fast  as 
it  is  made,  by  two  ducts  beginning  at  the  inner  angle  of 
the  eye,  one  on  each  lid ;  these  two  ducts  soon  unite  and 
empty  by  one  outlet  into  the  nasal  cavity.  If  these  ducts 
are  stopped,  or  if  the  secretion  be  formed  very  rapidly, 
the  liquid  overflows  on  the  face  as  tears. 

The  External  Parts  of  the  Eye.— The  " white  of  the 
eye  "  is  the  sclerotic  coat.  It  has  blood  tubes,  but  ordina- 
rily they  are  not  conspicuous.  The  front  part  of  the  eye- 
ball is  covered  with  the  cornea.  This  is  transparent,  and 
the  color  of  the  iris  shows  through  the  cornea.  In  the 
center  of  the  iris  is  the  hole,  or  pupil,  by  which  Jight  enters 
the  interior  of  the  eye. 

The  Conjunctiva.  —  The  front  of  the  eyeball  is  covered 
by  a  thin,  transparent,  mucous  membrane,  the  conjunctiva, 
which  turns  back  and  lines  the  inside  of  the  eyelids.  It  is 
highly  sensitive. 

The  Muscles  of  the  Eyeball.  —  There  are  six  muscles  which  move 
the  eyeball,  —  four  straight  muscles  (the  recti)  and  two  oblique.  The 
four  straight  muscles  arise  from  the  deepest  part  of  the  eye  socket  and 
pass  forward  to  be  attached  to  the  top,  bottom,  and  sides  of  the  ball. 
Where  they  are  attached,  they  are  flattened  out  like  straps.  The  in- 
ferior oblique  arises  from  the  inner  front  part  of  the  orbit  and  passes 
outward  to  attach  to  the  under  surface  of  the  eyeball.  The  superior 


THE  SENSE  OF  SIGHT,  287 

oblique  arises,  like  the  recti,  at  the  deeper  part  of  the  eye  socket  and 
passes  forward  through  a  fibre-cartilaginous  loop  or  pulley  near  the 
inner,  upper  angle  of  the  orbit,  and  then  runs  outward  and  is  attached 
to  the  upper  surface  of  the  eyeball. 

Movements  of  the  Eye.  — These  six  pairs  of  muscles  move  the 
eyes  to  right  and  left,  up  and  down,  and  give  rotary  movements. 
Normally  the  two  eyes  move  in  the  same  direction  at  the  same  time, 
though  in  looking  at  near  objects  the  two  eyes  both  point  inward,  so 
that  one  appears  cross-eyed,  and  in  looking  at  an  object  that  is  moving 
away  from  one,  the  eyes  are  gradually  diverging,  though  this  is  slight. 

Dissection  of  an  Eye.  —  The  muscles  and  external  parts  of  the  eye 
may  readily  be  seen  by  examining  the  eye  of  a  rabbit  in  its  natural 
position  and  then  dissecting  it  out.  A  beef  eye  should  be  obtained 
from  the  butcher  and  the  structure  of  the  eye  learned  by  following  the 
description  below. 

The  Coats  of  the  Eye.  —  There  are  three  coats,  the  outer 
or  sclerotic,  the  middle  or  choroid,  and  the  inner  called  the 
retina. 

The  Sclerotic  Coat.  —  This  is  of  a  dull  white  color,  con- 
stituting the  "white  of  the  eye."  It  is  thick  and  tough, 
holding  all  the  contained  parts  firmly  and  furnishing  suffi- 
cient strength  for  the  attachment  of  the  muscles  that  move 
the  eyeball. 

The  Choroid  Coat.  —  The  middle  layer  of  the  eye  coat 
is  the  choroid.  It  is  thinner  than  the  sclerotic  and  of  much 
more  delicate  structure.  It  is  permeated  by  blood  tubes, 
and  has  an  inner  lining  of  dark  color  to  prevent  the  reflec- 
tion of  light  in  the  eye,  just  as  most  optical  instruments 
are  painted  black  on  the  inside. 

The  Retina.  —  The  retina  is  a  continuation  and  expan- 
sion of  the  optic  nerve  and  forms  an  inner  coat  that  lines 
all  but  the  anterior  part  of  the  eye.  It  is  a  thin,  translu- 
cent film,  somewhat  like  the  film  that  forms  over  the  white 


288 


PHYSIOLOGY. 


of  an  egg  when  it  is  first  dropped  into  hot  water.  It  is 
exceedingly  delicate  and  easily  torn.  The  retina  is  the 
only  part  of  the  eye  that  is  sensitive  to  light,  and  on  it  the 
images  must  be  formed  to  produce  distinct  vision. 

The  Cornea. — The  clear  front  part  of  the  eye  is  the 
cornea.     It  is  a  continuation  of  the  sclerotic  coat  and  is 

Ciliary  Muscle 


Optic  Nerve  Choroid 

Fig  86.     Horizontal  Section  of  Right  Eye. 

more  bulging  than  the  rest  of  the  front  of  the  eye,  as  can 
be  seen  by  taking  a  side  view  of  the  eye,  or  by  noticing 
some  one  who  closes  the  eyelids  and  rolls  the  eyes  about. 

The  Iris.  —  This  is  the  part  that  gives  the  color  to  the 
eye,  or  if  the  pigment  that  gives  the  color  is  lacking,  the 
blood  gives  the  pink  color  seen  in  albinos.  The  iris  is  a 
forward  continuation  of  the  choroid  coat. 


THE  SENSE   OF  SIGHT.  289 

The  Pupil.  —  Most  of  the  light  that  passes  through  the 
transparent  cornea  is  stopped  by  the  opaque  iris.  But  in 
the  center  of  the  iris  is  a  round  hole  through  which  light 
enters  the  interior  of  the  eye.  The  pupil  looks  dark  be- 
cause it  is  the  only  opening  into  a  dark  room. 

Regulation  of  the  Amount  of  Light  admitted  into  the  Eye.— 

Hold  a  hand  glass  between  the  face  and  a  well-lighted  window.  Note 
the  size  of  the  pupils.  Quickly  turn  toward  the  darkest  part  of  the 
room.  We  see,  what  we  have  all  noticed  in  watching  the  eyes  of  a  cat, 
that  when  subject  to  a  bright  light  the  pupil  is  small,  but  with  less  light 
the  pupil  is  larger.  The  iris  has  circular  muscle  fibers  that  reduce  the 
pupil  when  there  is  too  much  light  for  the  eye,  and  when  the  light  is 
feeble  the  pupil  opens  wider. 

The  Refracting  Media  of  the  Eye.  —  The  media  that 
refract  the  rays  of  light  to  form  the  images  on  the  retina 
are  the  cornea,  the  aqueous  humor,  the  crystalline  lens,  and 
the  vitreous  humor.  The  cornea  has  already  been  described. 

The  Aqueous  Humor.  —  In  looking  at  the  entire  eye  it 
is  not  easy  to  realize  that  there  is  a  space  between  the  cor- 
nea and  the  iris.  In  this  space  is  the  clear,  watery  aque- 
ous humor. 

The  Vitreous  Humor.  —  All  but  the  front  part  of  the 
space  within  the  coats  of  the  eye  is  filled  with  a  clear, 
jellylike  substance,  the  vitreous  humor. 

The  Crystalline  Lens. —  Just  back  of  the  iris  is  a  double- 
convex  lens,  clear  as  crystal,  and  of  about  the  consistency 
of  a  gumdrop.  It  is  less  convex  on  the  front  surface. 

The  Lens  Capsule. — The  lens  is  completely  enveloped 
in  a  thin,  transparent  membrane  called  the  lens  capsule. 

The  Hyaloid  Membrane.  —  A  thin  membrane,  the  hya- 
loid membrane,  lines  the  inner  surface  of  the  retina.  As 
it  continues  forward  toward  the  lens  capsule  it  is  called 
the  suspensory  ligament. 


290  PHYSIOLOGY. 

The  Ciliary  Muscle.  —  Arising  from  the  sclerotic  coat, 
just  within  the  outer  border  of  the  iris,  is  the  ciliary  muscle. 
It  is  inserted  in  the  margin  of  the  lens  capsule  by  means 
of  fibrous  strands  that  form  an  intimate  part  of  the  capsule. 

Experiment  with  Lens  to  show  Inversion  of  Image.  —  Take  a 
double-convex  lens,  two  ot  which  are  in  the  common  "  tripod  lens,1'  or 


Fig.  87.    The  Formation  of  an  Image  on  the  Retina. 

any  hand  magnifier.  Hold  this  up  in  front  of  a  window  and  catch  the 
inverted  image  o/  the  window  on  a  piece  ot  paper  held  back  of  the  lens. 
This  illustrates  how  the  image  ot  an  external  object  is  formed  by  the 
crystalline  lens  upon  the  retina  ot  the  eye.  If  two  lenses  of  different 
thickness  can  be  obtained,  it  will  be  seen  that  the  thicker  lens  (if  both 
have  the  same  diameter)  will  make  an  image  closer  to  the  lens  than  the 
thinner  one. 

Experiments  to  illustrate  the  Adjustment  for  Distance.  —  (i )  Stick 
a  pin  at  each  end  of  a  book  cover.  Hold  the  book  at  about  the  usual 
distance  for  reading,  so  that  the  two  pins  are  in  a  line  with  the  eye. 
Look  closely  at  the  nearer  pin,  and  the  second  pin  will  appear  indistinct. 
Now  look  closely  at  the  head  of  the  farther  pin.  The  nearer  one  may 
be  seen,  but  not  sharply.  (2)  Hold  the  tip  of  a  pencil  in  a  line  with  any 
object,  say  a  picture,  on  a  wall  opposite.  In  looking  at  the  tip  of  the 
pencil  the  picture  is  dim.  Now  look  by  the  pencil  at  the  picture,  and 
the  point  of  the  pencil  will  be  blurred. 

Adjustment  of  the  Lens  for  Seeing  at  Different  Dis- 
tances. —  If  we  look  up  from  a  book  we  are  reading,  we 
do  not  realize  that  any  change  is  necessary  in  the  eye  for 
us  to  see  a  distant  object.  But  the  above  experiments 
prove  that  we  cannot,  at  the  same  time,  see  distinctly  a 
near  and  a  distant  object.  When  the  photographer  places 
his  camera,  he  moves  the  ground-glass  plate  back  and  forth 
till  the  image  is  distinctly  formed  on  the  plate.  We  cannot 


THE  SENSE   OF  SIGHT. 


291 


move  the  retina  back  and  forth,  so  we  change  the  shape  of 
the  lens.  When  we  look  at  a  near  object  the  lens  becomes 
thicker,  and  when  we  look  at  a  distant  object  the  lens  be- 
comes less  thick.  This  adjustment  is  called  accommodation. 


CILIARY  MUSCLE 


FAR  NEAR  CILIARY  PROCESS 

Fig.  88.     A  Diagram  to  illustrate  Accommodation.  » 

Action  of  the  Ciliary  Muscle.  —  In  looking  at  a  near  object,  the 
ciliary  muscle  pulls  on  the  hyaloid  membrane,  and  draws  it  forward 
(since  the  muscle  is  fastened  at  the  point  where  the  iris  joins  the 
cornea).  When  the  hyaloid  membrane  is  pulled  forward,  the  lens  is 
released  from  pressure  that  was  given  it  by  the  lens  capsule.  Now  the 
lens  becomes  thicker  because  it  is  elastic,  and  when  it  is  not  subject  to 
pressure  it  tends  to  become  relatively  thick.  When  we  look  at  a  dis- 
tant object  the  muscle  relaxes,  and  the  capsule  presses  on  the  front  of 
the  lens  and  flattens  it,  thus  adjusting  for  far  sight.  It  should  be 
noted  that  adjustment  for  near  sight  is  brought  about  by  muscular 
effort,  hence  is  fatiguing ;  whereas  adjustment  for  far  sight  is  accom- 
plished mechanically,  without  effort. 


(2)   Near-sighted   Eye.  (I)   Normal    Eye.  (3)    Far-sighted   Eye. 

Fig.  89.     Defects  in  Eyesight. 

Defects  of  Eyesight.  —  In  old  age  the  lens  usually  be- 
comes less  elastic, -and  cannot  adjust  for  near  sight.     Since 


292 


PHYSIOLOGY. 


it  is  unable  to  grow  more  convex,  artificial  lenses  (eye- 
glasses) may  be  used  to  enable  one  to  see  near  objects 
clearly.  Most  elderly  people  see  fairly  well  at  a  distance, 
but  use  glasses  for  reading  or  any  close  work.  In  "  near- 
sighted "  eyes,  the  eyeball  is  often  too  long  from  front  to 
back,  so  the  rays  meet  in  front  of  the  retina.  Concave 
glasses  remedy  this  defect.  The  eye  may  also  be  too 
short  (far-sighted)  and  need  convex  glasses.  The  refract- 
ing surfaces  (cornea  and  lens)  may  be  unequally  curved, 
causing  astigmatism.  For  most  of  these  defects  the 
oculist  can  supply  suitable  glasses. 


Inner  or  Vitreous  Surface 


Internal  Limiting  Layer 
Layer  of  Nerve  Fibers 
Layer  of  Nerve  Cells 


Inner  Molecular  Layer 


Inner  Nuclear  Layer 
Outer  Molecular  Layer 

—  Outer  Nuclear  Layer 

External  Limiting  Layer 

Layer  of  Rods  and  Cones 

~  Layer  of  Pigment  Cells 

Outer  or  Choroid  Surface 

Fig.  90.    Diagrammatic  Section  of  the  Human  Retina.    (Waller.) 

The  Structure  of  the  Retina.  — The  retina  is  very  complicated  in 
its  structure.  No  less  than  eight  layers  have  been  distinguished,  as 
shown  in  Fig.  90.  Of  these  layers  the  outermost,  the  layer  of  the  rods 
and  cones,  is  the  one  directly  concerned  in  appreciating  the  differences 
in  the  vibrations  of  the  light.  The  rays  of  light  pass  through  the 


THE  SENSE  OF  SIGHT.  293 

retina,  and  produce  their  effect  on  the  rods  and  cones  which  constitute 
the  outer  (back)  layer;  and  the  nerve  impulses  aroused  by  the  light 
must  return  through  the  thickness  of  the  retina  to  be  conveyed  along 
the  nerve  fibers  of  the  innermost  layer  of  the  retina  to  the  optic  nerve. 

Importance  of  the  Retina.  —  The  chief  structure  in  the 
eye  is  the  retina.  Without  this  all  else  is  useless.  If 
light  of  sufficient  strength  falls  on  the  retina,  it  stimulates 
elements  in  the  outer  layer  (rods  and  cones),  and  the  nerve 
impulses,  thus  started,  pass  along  the  fibers  of  the  optic 
nerve  to  the  brain,  and  we  have  the  sensation  of  sight. 
But  in  order  to  see  anything  distinctly,  the  light  must  fall 
on  the  retina  in  such  a  way  as  to  form  a  distinct  image  of 
that  object.  If  the  lens  be  removed,  or  becomes  opaque, 
as  in  "  cataract,"  we  fail  to  see  distinctly,  though  we  may 
discern  light  from  darkness.  The  other  parts  of  the  eye 
exist  to  form  images  oh  the  retina.  The  cornea,  lens,  and 
the  aqueous  and  vitreous  humors  are  the  parts  directly  con- 
cerned in  forming  the  images.  Light  from  an  object  passes 
through  the  cornea,  aqueous  humor,  lens,  and  vitreous 
humor,  and  the  rays  are  so  refracted  as  to  form  an  inverted 
image.  If  this  image  falls  on  a  good  retina,  we  see  well. 

The  Blind  Spot.— The  retina  is  much  more  complicated  than  any 
of  the  other  nerve  endings.  Light  must  fall  on  these  special  structures 
to  have  any  effect.  Falling  on  the  optic  nerve  itself  has  no  effect  in 
giving  a  sensation  of  light.  And  if  the  light  falls  on  the  spot  where 
the  optic  nerve  enters  the  eyeball  we  see  nothing.  Hence,  this  spot  is 
called  the  blind  spot. 

Experiment  illustrating  the  Blind  Spot.  —  At  the  left  (as  looked 
at  by  the  class)  of  a  long  blackboard  make  a  bright  circular  spot,  three 
inches  in  diameter,  with  white  or  yellow  crayon.  Beginning  at  the 
right  of  this  write  the  figures  i,  2,  3,  etc.,  along  the  whole  length  of  the 
board,  about  eight  inches  apart.  Let  each  pupil  close  the  right  eye  and 
look  at  the  bright  spot.  Then  let  each  read  the  figures,  passing  slowly 
from  one  to  another  in  order,  at  the  same  time  noticing  whether  the 
bright  spot  can  be  seen.  To  succeed  in  this  the  eye  must  not  be  allowed 


294  PHYSIOLOGY. 

to  waver.  Have  the  pupils  tell  when  the  bright  spot  disappears,  then 
read  on,  and  note  when  the  soot  reappears. 

Another  Experiment.  —  In  this  experiment  shut  the  right  eye,  and 
be  careful  not  to  let  the  left  eye  waver. 

.  Read  this  line  slowly.  Can  you  see  the  star  all  the  time  ?  If  the 
star  does  not  disappear  before  reaching  the  end  of  the  line,  let  the  eye 
travel  on  across  the  right-hand  page,  or  hold  the  book  nearer  the  face. 
In  the  human  eye  the  optic  nerve  enters  the  eye  not  in  the  center,  but 
nearer  the  nose,  so  that  in  turning  the  left  eye  toward  the  right  at  the 
proper  angle,  the  image  of  the  star  falls  upon  the  spot  where  the  optic 
nerve  enters.  As  this  spot  is  insensitive  to  light,  the  star  no  longer 
appears. 

The  Optic  Nerve  not  Sensitive.  —  The  optic  nerve, 
while  capable  of  carrying  nerve  impulses  that  cause  sensa- 
tions of  light,  is  not  itself  sensitive  to  light.  If  the  optic 
nerve  be  cut,  it  does  not  give  pain,  but  gives  the  sensation 
of  a  flash  of  light. 

Sympathy  between  the  Two  Eyes. —While  most  of 
the  fibers  from  each  optic  nerve  cross  to  the  other  side  of 
the  brain,  some  fibers  go  to  the  same  side  of  the  brain. 
We  can  therefore  better  understand  the  close  sympathy 
that  we  know  exists  between  the  two  eyes. 

Pain  in  the  Eyes.  —  Pain,  felt  in  the  eyes,  comes  from 
impulses  conveyed,  not  by  the  optic  nerve,  but  by  a  branch 
of  the  fifth  pair  of  nerves  (the  nerves  of  sensation  for  most 
of  the  face). 

Color  Sensations.  —  The  difference  in  colors  is  due  to  the  differ- 
ences in  the  rapidity  of  the  vibrations  of  the  waves  of  light,  as  in  sound 
differences  in  the  rapidity  of  the  vibrations  of  the  sound  waves  cause 
the  various  degrees  of  pitch.  Many  interesting  experiments  may  be 
made  with  color  sensation,  most  of  which  are  difficult  of  explanation. 
Fasten  a  bright  red  wafer  or  seal  on  a  white  card.  Look  intently  at 
the  center  of  the  red  spot  till  the  eye  is  tired.  Then  quickly  look  at 
a  point  in  the  white  surface.  What  color  appears  ?  This  may  be 
repeated  with  other  colors. 


THE  SENSE  OF  SIGHT.  295 

Color  Blindness.  —  It  is  found  that  some  persons  can- 
not distinguish  certain  colors.  Blindness  to  red  and  green 
are  most  common.  This  is  a  matter  of  importance  among 
railroad  men  and  sailors  where  it  is  necessary  to  distinguish 
red  and  green  signals. 

Stereoscopic  Vision.  —  In  looking  at  an  object  with  one 
eye  more  is  seen  to  the  side  of  that  eye,  while  the  other 
eye  sees  more  of  the  other  side,  considerable  of  the  object 
being  seen  with  both  eyes.  The  effects  produced  on  the 
two  eyes  are  united,  and  so  we  better  see  objects  as  solids. 
This  is  what  is  termed  stereoscopic  or  binocular  vision. 

Duration  of  Impressions  of  Light.  —  Most  boys  have  amused  them- 
selves around  a  bonfire  by  whirling  a  stick  with  a  glowing  coal  on  its 
end.  The  continuous  circle  of  light  thus  produced  indicates  that  the 
impression  of  light  remains  for  a  time,  in  this  case  until  the  stick  com- 
pletes the  circle,  giving  a  continuous  line  of  light.  Or  when  riding  in  a 
carriage  the  spokes  of  the  wheels  blur  together  because  the  impression 
of  each  lingers  till  another  has  taken  its  place. 

After-Images.  — But  if  we  shut  the  eyes  quickly,  we  may  keep  dis- 
tinct the  impression  of  the  last  positions,  and  so  see  them  distinct  from 
each  other.  Better  still,  shut  the  eyes  while  looking  at  the  wheel,  then 
open  and  shut  them  as  quickly  as  possible. 

Again,  if  one  looks  at  a  bright  lamp  and  then  closes  the  eyes,  there 
may  remain  the  same  appearance  as  when  we  looked  at  the  object 
itself.  This  is  called  the  Positive  After-Image.  Or  sometimes,  espe- 
cially after  looking  long  at  a  bright  light,  we  may,  on  closing  the  eyes 
or  looking  away,  see  a  dark  spot  of  the  same  shape  as  the  bright  one  we 
looked  at.  This  is  called  the  Negative  After-Image. 

THE  CARE  OF  THE   EYES. 

i.  Objectionable  Light.  —  In  reading  we  wish  light 
from  the  printed  page.  Hence  we  should  avoid  light 
entering  the  eye  from  any  other  source  at  this  time.  While 
reading,  then,  do  not  face  a  window,  another  light,  a  mirror, 


296  PHYSIOLOGY. 

or  white  wall,  if  it  can  be  avoided.  White  walls  are  likely 
to  injure  the  eyes.  Choose  a  dark  color  for  a  covering  for 
a  reading  table.  Sewing  against  the  background  of  a  white 
apron  has  worked  serious  harm.  Direct  sunshine  very 
near  the  book  or  table  is  likely  to  do  harm. 

2.  Position  in  Reference  to  Light.  —  Preferably  have 
the  light  from  behind  and  above.     Many  authors  say  "  from 
the  left,"  or  "over  the  left  shoulder."     In  writing  with  the 
usual  slant  of  the  letters  this  may  be  desirable.     But  ver- 
tical writing  is  now  strongly  advocated,  as  it  enables  one 
to  sit  erect,  and  have  the  light  from  above  and  equally  for 
the  two  eyes.     Sitting  under  and  a  little  forward  of  a  hang- 
ing lamp  will  thus  give  the  light  equally  to  the  two  eyes 
and  send  no  light  direct  into  the  face.     In  reading  by  day- 
light avoid  cross-lights  so  far  as  possible. 

3.  Electric  Light. — The   incandescent   electric   light 
has  an  advantage  in  being  readily  lighted,  without  matches, 
and  in  giving  out  little  heat ;    but  owing  to  its  irregular 
illumination  (due  to  the  shadow  cast  by  the  wire  or  fila- 
ment), it  is  not  well  suited  for  study  or  other  near  work. 
For  this  purpose  an  Argand  gas  or  kerosene  burner  is 
much  to  be  preferred,  since  it  throws  a  soft,  uniform,  and 
agreeable  light  upon  the  work. 

4.  Reading  Outdoors.  —  Reading  out-of-doors  is  likely 
to  injure  the  eyes,  especially  when  lying  down.     To  try  to 
read  while  lying  in  a  hammock  is  bad  in  many  ways.     Too 
much  light  directly  enters  the  eye,  and  often  too  little  falls 
upon  the  printed  page. 

5.  Reading  Heavy  Books. — Do  not  hold  the  book  or 
work  nearer  the  eyes  than  is  necessary.  "  So  far  as  possible 
avoid  continuous  reading  in  large  or  heavy  books  by  arti- 


THE  SENSE   OF  SIGHT,  297 

ficial  light.  Such  books  being  hard  to  hold,  the  elbows 
gradually  settle  down  against  the  sides  of  the  body,  and 
thus  the  book  is  held  too  close  to  the  eyes,  or  at  a  bad 
angle,  or  the  body  assumes  a  bad  position. 

6.  Resting  the  Eyes.  —  Frequently  rest  the  eyes  by 
looking  up  and  away  from  the  work,  especially  at  some 
distant  object.     One  may  rest  the  eyes  while  thinking  over 
each  page  or  paragraph,  and  thus  really  gain  time  instead 
of  losing  it. 

7.  Strength  of    Light.  —  Have    light  that  is   strong 
enough.     Remember  that  the  law  of  the  intensity  of  light 
as  affected  by  distance  is  that  at  twice  the  distance  the 
light  is  only  one  fourth  as  strong.     Reading  just  before 
sunset  is  not  wise,     One  is  often  tempted  to  go  on,  not 
noticing  the  gradual  diminution  of  light. 

8.  Evening  Reading.  —  In  all  ways  endeavor  to  favor 
the  eyes  by  doing  the  most  difficult  reading  by  daylight, 
and  saving  the  better  print  and  the  books  that  are  easier 
to  hold  for  work  by  artificial   light.     Writing   is  usually 
much  more  trying  to  the  eyes  than  reading.     By  carefully 
planning  his  work  the  student  may  economize   eyesight, 
and  it  is  desirable   that  persons  blessed  with  good  eyes 
should  be  careful,  as  well  as  those  who  have   a   natural 
weakness  in  the  eyes.     It  often  results  that  those  inherit- 
ing weak  organs,  by  taking  proper  care,  may  outlast  and 
do  more  and  better  work  than    those  naturally  stronger, 
but  who,  through  carelessness,  injure  organs  by  improper 
use  or  wrong  use  (ab-use). 

9.  Artificial  Light  in  the  Morning.  —  Reading  before 
breakfast  by  artificial  light  is  usually  bad. 


2Q8  PHYSIOLOGY. 

10.  Reading  during  Convalescence.  —  Many  eyes  are 
ruined  during  convalescence.  At  this  time  the  whole  sys- 
tem is  often  weak  —  including  the  eyes.  Still,  there  is  a 
strong  temptation  to  read,  perhaps  to  while  away  the  time, 
perhaps  to  make  up  for  lost  time  in  school  work.  This  is 
a  time  when  a  friend  may  show  his  friendship. 

u.  Irritation  of  the  Eyes.  —  If  one  finds  himself  rub- 
bing his  eyes,  it  is  a  clear  sign  that  they  are  irritated.  It 
may  be  time  to  stop  reading.  At  any  rate,  one  should  find 
the  cause,  and  not  proceed  with  the  work  unless  the  irrita- 
tion ceases.  If  any  foreign  object,  as  a  cinder,  lodges  in 
the  eye,  it  is  better  not  to  rub  the  eye,  but  to  draw  the  lid 
away  from  the  eyeball  and  wink  repeatedly ;  the  increased 
flow  of  tears  may  dissolve  and  wash  the  matter  out.  To 
relieve  the  feeling  that  something  must  be  done  it  may  be 
well  to  rub  the  other  eye,  but  of  course  this  gives  no  posi- 
tive relief  to  the  affected  eye.  If  it  be  a  sharp  cornered 
cinder,  rubbing  may  merely  serve  to  fix  it  more  firmly  in 
the  conjunctiva.  If  it  does  not  soon  come  out,  the  lid  may 
be  rolled  up  over  a  pencil,  taking  hold  of  the  lashes  or  the 
edge  of  the  lid.  The  point  of  a  blunt  lead  pencil  is  a  con- 
venient and  safe  instrument  with  which  to  remove  the  par- 
ticle. Sometimes  being  out  in  the  wind  (especially  if  un- 
used to  it),  together  with  bright  sunlight,  may  irritate  the 
eyes.  If  after  such  exposure  one  finds  lamplight  irritating, 
he  will  do  well  to  go  to  bed  early,  or  remain  in  a  dark 
room. 

12.  Keep  the  Eyes  Clean.  —  Be  careful  to  keep  the 
eyes  clean.  Do  not  rub  the  eyes  with  the  fingers.  Aside 
from  consideration  of  rules  of  etiquette,  there  is  danger  of 
introducing  foreign  matter  that  may  be  very  harmful.  It 
is  very  desirable  that  each  person  have  his  individual  face 


THE  SENSE  OF  SIGHT.  299 

towel.     By  not  observing  this  rule  certain  contagious  dis- 
eases of  the  eyes  often  spread  rapidly. 

13.  Consult  a  Reliable  Oculist. —  If  there  is  any  con 
tinuous  trouble  with  the  eyes,  consult  a  reliable  oculist. 
Many  headaches  are  due  to  eye-strain,  the  real  cause  being 
unsuspected.  If  a  child  has  frequent  headaches,  it  is  well 
to  have  the  eyes  examined.  Many  persons  injure  their 
eyes  by  not  wearing  suitable  glasses.  On  the  other  hand, 
do  not  buy  glasses  of  peddlers  nor  of  any  but  reliable 
specialists.  One  may  ruin  the  eyes  by  wearing  glasses 
when  they  are  not  needed.  Sight  is  priceless. 

READING.  —  Sight,  Le  Conte. 


Summary.  —  i.    Sight,  like  hearing,  acts  through  space,  outstripping 
the  "contact  senses  "  of  touch,  taste,  and  smell. 

2.  The  eye  is  protected  by  its  bony  surroundings,  lids,  lashes,  tears, 
sensitiveness  of  the  conjunctiva,  etc. 

3.  The  eye  is  moved  by  muscles  under  nerve  control. 

4.  The  eye  has  three  coats  —  sclerotic,  choroid,  and  retina. 

5.  The  pupil  is  a  hole  in  the  iris,  and  varies  in  size  to  regulate  the 
amount  of  light  admitted. 

6.  The  refracting  media  of  the  eye  are  the  cornea,  aqueous  humor, 
lens,  and  vitreous  humor. 

7.  These  refracting  media  form  an  inverted  image  on  the  retina. 
The  eye  is  a  camera,  darkened  on  the  inside. 

8.  The  ciliary  muscle,  acting  on  the  elastic  lens,  adjusts  the  lens 
for  seeing  at  different  distances. 

9.  Suitable  lenses  overcome  many  of  the  defects  in  eyesight. 

10.  The  retina  is  an  expansion  of  the  optic  nerve,  and  is  exceed- 
ingly complicated  in  its  structure. 

11.  The  blind  spot  is  the  place  where  the  optic  nerve  enters  the  eye. 

12.  The  optic  nerve  is  insensitive  to  light,  but  injury  to  it  causes 
sensations  of  light. 

13.  Most  of  the  fibers  of  the  optic  nerve  cross  to  the  other  half  of 
the  brain,  but  some  do  not  cross. 


300  PHYSIOLOGY. 

14.  Color  is  due  to  difference  in  the  rapidity  of  vibration  in  the 
waves  of  light. 

15.  Some  eyes  do  not  distinguish  these  differences  and  are  color 
blind. 

1 6.  Pain  in  the  eyes  comes  through  the  fifth  pair  of  nerves,  not 
through  the  optic  nerves. 

17.  Binocular  vision  makes  objects  "stand  out"  more  distinctly  as 
solid  bodies. 

1 8.  Impressions  of  light  linger,  making  after-images. 

19.  Defects  in  eyesight  are  much  more  common  among  civilized 
men  than  with  the  uncivilized  men  or  animals. 

20.  The  care  of  the  eyes  must  be  made  a  subject  of  study  and  care- 
ful thought  by  all  reading  people. 

Questions.  —  i.   What  iythe  position  of  the  eyeballs  during  sleep? 

2.  What  is  "cataract"? 

3.  What  is  the  cause  of  "  double  vision  "? 

4.  Why  does  the  well  eye  sympathize  with  the  affected  one? 

5.  Why  does  looking  at  a  bright  light  often  cause  a  person  to 
sneeze  ? 

6.  Why  is  weeping  associated  with  grief  ? 

7.  What  is  the  condition  of  one  who  is  "cross-eyed"? 

8.  Compare  the  pupils  of  a  man,  a  cat,  and  a  cow. 

9.  Does  the  color  of  the  eye  have  any  relation  to  the  strength  of 
eyesight  ? 

10.    Why  is  one  blinded  on  entering  a  bright  room  from  the  dark? 
n.    Why  is  one  going  from  a  bright  room  into  the  dark  unable  to 
see  at  first,  but  gradually  sees  more  distinctly  ? 

12.  Why  can  one  not  see  well  when  the  eye  "  waters  "? 

13.  If  each  eye  has  a  blind  spot,  why  are  there  'not  blank  spaces  in 
the  field  of  vision? 

14.  What  advantage  has  a  stereoscopic  view  over  a  single  view? 
How  are  stereoscopic  views  made? 

15.  Should  the  lights  which  illumine  a  pulpit  or  platform  be  so 
placed  that  they  can  shine  into  the  eyes  of  the  congregation?     How 
should  they  be  arranged? 


CHAPTER   XXL 
TASTE,  SMELL,  AND  HEARINGo 

Uses  of  the  Sense  of  Taste.  —The  sense  of  taste  helps 
us  in  judging  of  the  fitness  of  anything  that  presents  itself 
as  a  candidate  for  election  as  food.  By  reflex  action  the 
taste  of  agreeable  substances  aids  in  digestion  by  stimulat- 
ing the  glands,  especially  the  salivary  glands. 

The  Papillae.  —  The  surface  of  the  tongue  is  covered 
with  papillae.  These  are  of  three  kinds.  Most  numerous 


Papillae 


Glosso-pharyngeal 
Nerve  (9th) 


Gustatory  Branch  of  Fifth  Nerve 
Fig.  91.    Diagram  of  Tongue,  showing  Nerves  and  Papilla. 

are  the  filiform  papillae,  slender,  cylindrical  projections. 
Like  the  papillae  of  the  skin,  they  seem  to  be  organs  of 
touch.  Scattered  among  the  filiform  papillae  are  small, 
bright  red  spots  which,  on  examination,  are  found  to  be 
shaped  somewhat  like  a  mushroom,  the  fungiform  papillae. 
Near  the  base  of  the  tongue  are  about  a  dozen  larger  pa- 

301 


302  PHYSIOLOGY. 

pillae,  arranged  like  a  letter  V  with  its  apex  toward  the  base 
of  the  tongue.  These  are  the  circumvallate  papillae,  each 
having  around  it  a  deep  circular  furrow. 

The  Nerve  Supply  of  the  Tongue. — On  the  sides  of 
this  furrow  are  small  oval  bodies,  called  "  taste  buds,"  con- 
nected with  the  ends  of  the  nerves  of  taste.  The  nerves 
of  taste  are  the  glosso-pharyngeal,  or  ninth  cranial  nerves, 
distributed  to  the  back  part  of  the  tongue,  and  a  branch  of 
the  fifth  pair  of  nerves,  the  gustatory,  to  the  front  part. 

Although  we  ordinarily  speak  of  an  article  of  food  as 
"palatable,"  or  "unpalatable,"  the  sense  of  taste  in  the 
palate  is  only  feebly  developed.  The  tip  of  the  tongue 
seems  to  be  most  sensitive  to  sweets  and  salines,  the  back 
part  to  bitters,  and  the  sides  to  acids. 

Solution  Necessary  for  Tasting.  —  Substances  must  be 
dissolved  before  they  can  be  tasted.  If  the  tongue  be 
wiped  dry,  and  a  few  grains  of  salt  or  sugar  be  placed  on 
it,  the  taste  will  not  be  perceived  for  a  little  time.  Insol- 
uble substances  give  no  taste. 

Flavors.  —  What  we  call  flavors  affect  us  more  through 
the  sense  of  smell  than  through  taste.  If  the  nose  be  held 
shut,  and  we  are  careful  about  breathing,  a  piece  of  onion 
placed  on  the  tongue  does  not  produce  what  we  usually 
call  the  taste  of  the  onion.  We  may  thus  get  rid  of  the 
disagreeable  part  of  taking  certain  medicines.  Let  the 
student  experiment  with  various  substances  as  above  in- 
dicated. 

Effect  of  Temperature  on  Taste.  —  It  is  said  that  the 
temperature  of  about  40°  F.  is  most  favorable  for  tasting, 
and  after  rinsing  the  mouth  with  very  hot  or  very  cold 
water,  such  bitter  substances  as  quinine  will  have  only  a 
trace  of  their  usual  taste. 


TASTE,   SMELL,   AND  HEARING. 


303 


Olfactory  Nerves J 


Branches  of 
Fifth   Nerve 


Turbinated  Bones 


The  Sense  of  Smell.  —  "The  sense  of  odor  gives  us 
information  as  to  the  quality  of  food  and  drink,  and  more 
especially  as  to  the  quality  of  the  air  we  breathe.  Hence 
we  find  the  organ  placed  at  the  opening  of  the  respiratory 
passages,  and  in  close  proximity  to  the  organs  devoted  to 
taste.  Taste  is  at  the  gateway  of  the  alimentary  canal, 
just  as  smell  is  the  sentinel  of  the  respiratory  tract;  and 
just  as  taste,  when  combined  with  smell  to  give  the  sen- 
sation we  call 
flavor,  influ- 
ences the  di- 
gestive pro- 
cess, and  is 
influenced  by 
it,  so  smell 
influences  the 
respiratory  process.  The 
presence  of  odors  influ- 
ences both  the  amplitude 
and  the  number  of  the 
respiratory  movements. 
Thus  the  smell  of  winter- 
green  notably  increases  the 

respiratory  work,  next  comes  ylang-ylang,  and  last  rose- 
mary. The  breathing  of  a  fine  odor  is  therefore  not  only 
a  pleasure,  but  it  increases  the  amplitude  of  the  respira- 
tory movements.  Just  as  taste  and  flavor  influence  nutri- 
tion  by  affecting  the  digestive  process,  and  as  the  sight  of 
agreeable  or  beautiful  objects,  and  the  hearing  of  melo- 
dious and  harmonious  sounds  react  on  the  body  and  help 
physiological  well-being,  so  the  odors  of  the  country,  or 
even  those  of  the  perfumer,  play  a  beneficent  role  in  the 
economy  of  life."  —  M'KENDRICK  and  SNODGRASS. 


Fig.  92.     Nerves  of  the  Outer  Wall  of  the 
Nasal  Cavity. 


304  PHYSIOLOGY. 

Why  we  Sniff.  —  In  quiet  breathing  the  air  passes 
along  the  lower  air  passages  just  above  the  hard  palate. 
The  true  olfactory  passages  are  higher,  but  still  in  com- 
munication with  this  lower  passage.  When  we  wish  to 
test  the  quality  of  the  air,  we  sniff,  that  is,  make  a  sudden 
inspiration  by  jerking  the  diaphragm  down,  and  air  from 
the  outside  then  rushes  into  these  upper  nasal  passages, 
over  the  walls  of  which  the  nerves  of  smell,  the  olfactory 
nerves,  are  spread  in  the  mucous  membrane.  The  sudden 
rush  of  air  against  this  membrane  seems  to  aid  greatly  in 
detecting  the  odor.  The  nerves  have  peculiar  endings, 
and  it  is  not  known  just  how  the  substances  produce  their 
effect.  The  substances  must  be  in  a  very  finely  divided 
state,  probably  gaseous.  The  mucous  membrane  is  sup- 
plied with  mucus,  and  the  odorous  substance,  probably,  is 
first  dissolved  in  the  mucus.  The  lower,  or  respiratory, 
passages  have  a  more  abundant  blood  supply,  and  are 
redder  than  the  upper.  In  inflammation,  owing  to  their 
narrowness,  the  passages,  especially  the  upper,  are  often 
closed  by  contact  of  the  opposite  sides.  Substances  like 
ammonia  have  no  odor,  but  excite  the  tactile  nerves.  They 
are  often  spoken  of  as  having  a  "  pungent  "  odor,  but  are 
simply  irritants. 

The  Sense  of  Hearing.  — The  ear  passages  are  inclosed 
by  the  hard  bones  of  the  head.  The  ear  is,  in  consequence, 
difficult  to  dissect.  It  is  very  desirable  to  have  a  model 
of  the  ear.  The  ear  may  be  dissected  in  a  cat  or  rabbit  by 
following  the  accompanying  description.  It  will  take  time 
and  patience  to  trace  all  the  parts. 

The  Parts  of  the  Ear.  —  The  ear  is  a  much  more  com- 
plicated organ  than  would  naturally  be  supposed.  The 
parts  of  the  ear  are  the  external,  the  middle,  and  the  in- 
ternal ear. 


TASTE,   SMELL,   AND  HEARING. 


305 


The  External  Ear.  —  The  external  ear  gathers  the 
sound  waves,  and  directs  them  into  the  opening  of  the  ear, 
but  the  loss  of  the  external  ear  does  not  seriously  interfere 
with  hearing.  The  passage  leading  inward  from  the  ear 
extends  about  an  inch,  and  is  then  completely  shut  off 
from  the  cavities  beyond  by  a  thin  membranous  partition, 
the  tympanic  membrane  or  drum  skin.  The  skin  of  the 


Stirrup         Anv 


Semicircular  Canals 


COCHLEA 


PHARYNX 


Fig.  93.     Diagram  of  the  Ear. 


ear  dips  into  and  lines  the  external  tube,  and  continues  as 
a  very  thin  layer  over  the  membrane  of  the  tympanum. 
The  auditory  meatus,  as  this  passageway  is  called,  is 
guarded  by  hairs,  and  is  further  protected  by  wax  secreted 
by  glands  of  the  lining. 

The  Middle  Ear.  —  Beyond  the  membrane  of  the  tym- 
panum is  a  cavity  called  the  middle  ear.  Extending  across 
the  cavity  of  the  middle  ear  is  a  chain  of  very  small  bones, 
the  hammer,  anvil,  and  stirrup,  the  hammer  being  attached 


306  rnvsiOLOc,\. 

to  the  inner  surface  of  the  membrane  of  the  tympanum, 
and  the  stirrup  being  fastened  by  its  base  to  the  wall  of 
the  internal  ear. 

The  Eustachian  Tube.  — The  middle  ear  communicates 
with  the  pharnyx  by  means  of  a  narrow  tube  called  the 
eustachian  tube.  It  admits  air  to  equalize  the  pressure  on 
the  two  sides  of  the  tympanic  membrane.  This  tube  is 
probably  closed  most  of  the  time,  but  opens  when  we 
swallow. 

The  Internal  Ear.  —  The  internal  ear  consists  of  several 
complicated  cavities  and  tubes  which  contain  a  liquid  in 
which  rest  the  nerves.  The  principal  cavity  is  the  cochlea, 
or  snail-shell  cavity,  in  which  the  nerve  endings  are  con- 
nected with  an  exceedingly  complicated  apparatus. 

The  Production  of  Sound.  —  Sound  waves  set  the  drum 
skin  or  membrane  of  the  tympanum  in  vibration ;  the 
vibrations  are  conveyed  by  the  chain  of  bones  across 
the  middle  ear  to  the  liquid  of  the  inner  ear.  Through  the 
complicated  apparatus  of  the  snail  shell  the  vibrations  of 
the  liquid  are  made  to  start  nerve  impulses  in  the  fibers  of 
the  auditory  nerve,  and  when  these  nerve  impulses  are 
rightly  received  and  interpreted  by  the  brain,  we  have  a 
sensation  called  sound. 

The  Equilibrium  Sense.  —  Probably  most  of  the  senses  contribute 
to  the  maintaining  of  the  equilibrium  of  the  body  by  giving  information 
as  to  position,  motion,  etc.,  especially  sight  and  the  muscular  sense. 

Only  that  part  of  the  auditory  nerve  which  is  distributed  in  the 
"snail  shell"  of  the  ear  is  now  supposed  to  have  to  do  with  hearing. 
It  is  no  longer  believed  that  the  semicircular  canals  are  concerned  with 
the  process  of  hearing.  There  seems  to  be  good  evidence  that  the 
semicircular  canals  inform  us  as  to  changes  of  the  position  of  the  body, 
and  they  are  regarded  as  the  seat  of  an  "equilibrium  sense."  The  fact 
that  one  of  these  canals  is  horizontal,  and  that  the  two  vertical  canals 


TASTE,   SMELL,   AND  HEARING.  307 

are  at  right  angles  to  each  other,  strengthens  this  belief.  It  is  thought 
that  each  of  these  canals  detects  movements  in  its  own  plane.  The 
experiment  has  been  made  of  placing  a  man  on  a  table  that  easily 
turned ;  with  the  eyes  shut  the  subject  could  usually  detect  fairly  well 
the  changes  of  position  from  rotation  of  the  table.  What  is  known  on 
the  subject  comes  partly  from  observation  in  cases  where  these  parts 
are  diseased  (which,  in  itself,  does  not  cause  loss  of  hearing),  and  by 
operating  on  lower  animals ;  in  both  of  these  lines  of  observation 
injury  to  these  parts  appears  to  be  followed  by  dizziness,  loss  of  power 
to  maintain  equilibrium,  etc. 

The  Care  of  the  Ear.  —  In  cleaning  the  ear  no  hard 
substance  should  be  used ;  even  the  finger  nail  is  likely  to 
do  harm.  A  moistened  cloth  should  be  used.  If  this  is 
not  sufficient,  a  physician  should  be  consulted.  In  wash- 
ing the  ear  it  should  be  thoroughly  dried  before  being 
exposed  to  a  wind,  especially  a  cold  wind.  The  rapid 
evaporation  may  cool  the  parts  so  rapidly  as  to  cause 
trouble.  It  is  not  well  to  stuff  the  ears  with  cotton.  If 
there  is  any  trouble  with  the  hearing,  of  course  a  physician 
should  be  consulted  without  delay. 

Colds  and  Deafness.  —  A  cold  often  produces  inflam- 
mation of  the  mucous  membrane  of  the  pharnyx.  This 
inflammation  may  extend  along  the  eustachian  tube  to  the 
middle  ear  and  affect  the  hearing. 

The  Use  of  the  Ears.  —  The  existence  of  an  organ  of 
hearing  implies  the  existence  of  what?  Why  have  we 
these  organs  of  hearing  ?  Is  it  merely  a  means  of  protec- 
tion ?  Is  it  that  we  may  enjoy  the  music  of  nature,  such 
as  the  songs  of  birds  ?  Is  there  not  one  sound  that  makes 
sweeter  music  than  the  most  gifted  of  feathered  songsters, 
surpassing  all  the  instruments  of  man's  device,  even  the 
violin,  with  its  almost  human  flexibility  and  range  of 
expression  ? 


308 

What  sound  communicates  to  us  the  most  of  thought 
and  sympathy  ? 

What  sound  was  it  Robinson  Crusoe,  in  his  dreary  soli- 
tude, most  longed  to  hear  ? 

READING.  —  The  PJiysiology  of  tlie  Senses,  M'Kendrick 
and  Snodgrass. 


Summary.  —  i.   Taste  enables  us  to  judge  of  the  quality  of  food, 
and  it  indirectly  influences  digestion. 

2.  The  tongue  has  two  nerves  of  taste,  the  fifth  pair  of  cranial  nerves 
supplying  the  front,  and  the  ninth  pair  the  base. 

3.  So-called  flavors  affect  the  sense  of  smell  more  than  that  of  taste. 

4.  The  sense  of  smell  tests  food  and  air. 

5.  Agreeable  odors  promote  respiration. 

6.  The  ear  consists  of  the  outer,  middle,  and  inner  ear.    In  the  inner 
ear  are  the  endings  of  the  auditory  nerve. 

7.  The  semicircular  canals  have  to  do  with  a  sense  of  equilibrium 
and  not  with  hearing. 

8.  Colds  and  catarrh  often  seriously  affect  hearing. 

Questions.  —  i.   How  may  the  sense  of  taste  be  blunted  ? 

2.  What  is  the  effect  of  inhaling  menthol  ? 

3.  Does  a  person  who  is  deaf  in  one  ear  hear  "  half  as  well "  as 
before  ? 

4.  Which  of  the  senses  goes  to  sleep  first  when  we  go  to  bed  ? 

5.  In  what  order  do  the  other  senses  go  to  sleep  ? 

6.  In  what  order  do  the  senses  waken  in  the  morning  ? 


CHAPTER   XXII. 
THE  VOICE. 

The  Ear  and  the  Voice.  —  The  delicate  mechanism  and 
capabilities  of  the  ear  are  fully  matched  by  the  fine  adjust- 
ment and  range  of  the  voice.  The  organ  of  the  voice  is 
well  worthy  of  study,  if  we  look  at  it  merely  as  a  most 
ingenious  contrivance,  to  say  nothing  of  its  importance  to 
us  as  a  means  of  expressing  thought. 

What  we  can  learn  from  Our  Own  Throats.  —  We  can  learn  a 
little  from  the  observation  of  our  own  mouths  and  throats.  The  pro- 
jection of  the  throat  known  as  "  Adam's  Apple  "  is  one  angle  of  the 
Thyroid  cartilage.  A  ridge  may  be  felt  running  downward  from  the 
projecting  angle.  Above  the  Adam's  apple  a  depression  may  be  felt. 
Press  the  tip  of  the  ringer  lightly  into  this  depression  and  perform  the 
act  of  swallowing.  It  will  be  noted  that  the  Adam's  apple  is  drawn  up- 
ward and  closer  to  the  bone  above  the  depression.  This  bone  is  the 
Hyoid  bone ;  it  is  connected  with  the  larynx  below  the  base  of  the 
tongue.  Below  the  thyroid  cartilage  another  cartilage  may  be  felt, 
the  Cricoid  cartilage.  Below  this  is  the  windpipe  with  its  rings  of 
cartilage.  The  general  form  of  the  whole  larynx  may  be  felt  in  a  per- 
son not  overburdened  with  fat. 

By  depressing  the  tongue  and  looking  into  the  mouth  the  tip  of  the 
epiglottis  may  possibly  be  seen  at  the  base  of  the  tongue.  Beyond 
these  points  we  cannot  learn  much  without  dissection.  A  small  mirror 
set  obliquely  on  a  handle  (like  those  used  by  dentists)  may  be  inserted 
through  the  mouth  so  that  the  larynx  can  be  seen  from  above.  But 
the  meaning  of  what  would  be  thus  seen  would  not  be  very  clear  with- 
out a  careful  dissection  of  the  larynx. 

The  Vocal  Cords.  —  The  vocal  cords  are  not  very  appro- 
priately named.  They  are  mere  ridges  projecting  from 

3°9 


3io 


PHYSIOLOGY. 


the  sides  of  the  larynx.  Under  the  covering  of  mucous 
membrane  are  ligaments  and  muscles  that  may  be  stretched 
to  various  degrees  and  placed  in  different  positions,  accord- 
ing to  the  sound  that  is  to  be  produced. 

The   Position  of   the  Vocal  Cords. —  While  we  are 

quietly  breathing,  the  vocal  cords,  or  bands,  lie  back,  like 
low  ridges,  against  the  side  of  the  larynx,  and  offer  nearly 
the  whole  channel  of  the  larynx  for  the  free  passage  of  air 


— Tiachca 

FROM    RIGHT  TO   LEFT  MEDIAN 

Fig.  94.    Longitudinal  Sections  of  the  Larynx. 

for  breathing  purposes.  But  when  we  wish  to  produce 
vocal  sound,  the  vocal  cords  are  made  to  stand  out  farther 
from  the  side  walls,  and  interfere  with  the  free  passage  of 
the  air.  In  examining  the  larynx,  it  is  seen  that  the  vocal 
cords  are  attached  close  to  each  other  in  front,  but  that  at 
the  back  of  the  larynx  they  diverge  widely  (in  the  position 
of  rest),  forming  a  letter  V,  with  the  angle  of  the  V  in 
front,  just  back  of  Adam's  apple.  "  When  changes  in  the 
voice  or  in  breathing  are  being  made,  the  white  glistening 


THE   VOICE.  311 

vocal  cords  may  be  seen  to  come  together  or  to  go  apart 
like  the  blades  of  a  pair  of  scissors."  In  a  high  note  the 
cords  are  close  together  and  nearly  parallel.  As  the  air 
is  forced  past  the  approximated  edges  of  the  vocal  cords, 
they  are  set  in  vibration,  and  produce  the  sound  called  the 
voice. 

Illustration  of  the  Vocal  Cords.  —  The  principle  of  the  action  of 
the  vocal  cords  can  be  illustrated  by  the  common  toy  known  as  the 
squeaking  balloon,  or  "squawker."  Here  the  air  is  driven  out  past  a 
band  of  rubber  stretched  across  the  inner  end  of  the  tube.  If  instead 


Epiglottis 
False  Vocal  Cords  ... 

True  Vocal  Cords  ~ 


i 
Glottis  Narrowed,  High  Note  Glottis  Wider,  Quiet  Breathing 

Fig.  95.    The  Larynx,  as  seen  by  Means  of  the  Laryngoscope,  in  Different 
Conditions  of  the  Glottis. 

of  one  band  with  both  edges  free,  we  were  to  tie  on  the  inner  end  of 
the  tube  two  bands  of  rubber,  each  covering  the  outer  edge  of  the  tube, 
leaving  the  inner  edge  of  the  rubber  free,  and  with  the  two  bands  touch- 
ing at  one  end  and  considerably  separated  at  the  other  end,  we  would 
have  a  pretty  fair  resemblance  to  the  larynx. 

Reenforcement  of  Vocal  Sound.  —  As  in  many  musical 
instruments,  the  vibrations  of  the  membrane  alone  would 
be  too  feeble  to  have  much  effect.  In  the  violin,  piano, 
drum,  etc.,  the  vibrations  are  reenforced  by  the  vibration 
of  a  body  of  air  contained  within.  So  here  the  vibrations 
of  the  cords  are  reenforced  and  modified  by  the  air  spaces 
above. 

Loudness  of  Voice.  —  The  loudness  of  the  voice  depends 
on  the  force  with  which  the  air  is  driven  past  the  cords, 


312  PHYSIOLOGY. 

together  with  the  size  and  condition  of  the  cords  them- 
selves. 

Pitch  of  Voice.  —  Pitch  depends  on  the  rapidity  of  the 
vibrations,  which  is  determined  by  the  length  of  the  cords 
and  their  tension.  Other  things  being  equal,  the  size  of 
the  larynx  would  determine  the  pitch. 

Voice  and  Speech. — The  larynx  by  itself  produces 
vocal  sound  merely.  In  speech  the  sounds  produced  in* 
the  larynx  are  much  modified  by  the  lips,  tongue,  teeth, 
cheeks,  etc.  We  have  voice  as  soon  as  born,  but  we  only 
gradually  acquire  the  power  of  speech.  Mammals,  birds, 
and  some  of  the  lower  vertebrates  have  voices,  but  they 
have  not  speech.  This  distinguishes  man  from  the  ani- 
mals below  him,  though  perhaps  some  of  the  higher  apes 
have  speech  in  a  slight  degree.  Dogs  can  express  their 
wants  by  barking,  growling,  snarling,  etc.,  but  it  is  mostly 
by  their  tone,  with  their  attitudes,  and  a  slight  facial 
expression  (as  in  snarling). 

Vowels  and  Consonants.  —  By  various  positions  of  the  tongue  and 
organs  of  the  throat  we  make  the  different  vowel  sounds.  In  the  con- 
sonants we  more  or  less  shut  off  (for  the  time)  the  passage  of  air,  and 
so  stop,  or  modify,  the  sound.  This  is  hardly  the  place  to  study  and 
analyze  the  sounds  of  our  spoken  language,  yet  it  may  be  found  profita- 
ble to  watch  the  different  organs  as  each  sound  is  produced  ;  for  when 
the  structure  and  relation  of  the  different  parts  concerned  in  the  pro- 
duction of  these  sounds  are  better  known,  the  definitions  and  state- 
ments of  the  books  will  be  much  more  fully  understood. 

Differences  between  Voices.  —  Since  no  two  throats 
are  exactly  alike,  no  two  voices  sound  just  the  same.  The 
size  and  shape  of  the  pharynx,  the  shapes  and  positions  of 
the  teeth,  lips,  the  condition  of  the  mucous  membrane  of 
the  passages  generally,  all  affect  the  sound,  and  give  it  its 
"  quality,"  by  which  we  distinguish  one  voice  from  another, 


THE   VOICE.  313 

even  if  they  are  in  the  same  pitch   and  have  the    same 
degree  of  loudness. 

Change  of  Voice.  —  At  about  the  age  of  fourteen  a  boy's  larynx 
increases  in  size  and  the  voice  changes,  becoming  deeper  and  heavier. 
During  the  change  the  falsetto  often  breaks  in  upon  the  ordinary  voice, 
the  voice  being  said  to  "  crack.'1 

Hoarseness.  —  If  the  mucous  membrane  covering  the  vocal  cords  is 
inflamed,  or  covered  with  too  much   mucous,  hoarseness  is  likely  to 
.result. 

Whispering.  —  As  in  the  animal  we  have  voice  without  speech,  so 
in  whispering  we  have  speech  without  voice ;  that  is,  there  is  no  vocali- 
zation. The  organs  of  speech  so  modify  the  aspiration  as  to  produce 
speech.  There  is  no  true  voice. 

Culture  of  the  Voice.  —  The  voice  and  speech  are 
very  susceptible  of  culture,  and  nearly  all  voices  may  im- 
prove by  proper  cultivation.  A  cultivated  voice  and  care- 
ful, distinct  speech  are  very  desirable  accomplishments, 
and  are  not  nearly  so  common  as  they  ought  to  be.  We 
delight  in  fine  singing,  and  many  strive  to  cultivate  this 
art ;  but  not  so  many  try  to  learn  to  talk  so  that  it  is  a 
pleasure  to  .hear  the  spoken  sound. 

READING.  —  The  Throat  and  the  Voice,  Cohen. 


Summary.  —  i.  The  larynx  is  very  complicated.  Various  muscles 
move  the  cartilages  and  vary  the  length  and  tension  of  the  vocal  cords, 
and  thus  produce  the  varying  degrees  of  pitch. 

2.  The  vocal  cords  are  not  simple  cords,  but  are  band-like  ridges 
on  the  sides  of  the  larynx. 

3.  The  higher  animals  have  voice  but  not  speech. 

4.  Whispering  is  speech  without  voice. 

5.  The  larynx  is  affected  by  "  colds  "  and  catarrh. 

Questions.  —  i.  Why  does  one  become  hoarse  from  hearing  others 
shouting? 

2.    What  is  ventriloquism? 


CHAPTER   XXIII. 
ACCIDENTS.— WHAT  TO  DO  TILL  THE  DOCTOR  COMES. 

How  to  Stop  Flow  of  Blood  from  Arteries.  —  In  case 
of  bleeding  from  an  artery  the  blood  comes  in  jets.  Pres* 
sure  should  be  applied  between  the  cut  and  the  heart.  To 
know  where  to  apply  the  pressure,  study  of  the  course  of 
the  main  arteries  should  be  made.  By  studying  Fig.  16 
it  will  be  seen  that  the  arteries  to  the  arms  pass  down  the 
inside  of  the  upper  arm.  Here  they  come  near  the  sur- 
face. At  the  elbow  the  artery  is  near  the  skin  in  the 
angle  of  the  elbow.  The  artery  which  makes  the  pulse  at 
the  wrist  is  well  known.  By  putting  a  baseball  under  the 
armpit  and  pressing  the  arm  down  firmly,  the  artery  may 
be  compressed. 

Bleeding  from  the  Upper  Arm.  —  In  case  of  a  deep 
cut  in  the  lower  part  of  the  arm,  a  handkerchief  should 
have  a  knot  tied  in  it,  and  the  knot  placed  over  the  artery ; 
that  is,  on  the  inside  of  the  arm  just  below  the  armpit. 
Pass  the  handkerchief  around  the  arm  and  tie  it  loosely. 
Then  run  a  stick  through  it,  and  twist  till  the  knot  is  drawn 
tightly  against  the  artery.  Instead  of  a  knot,  a  potato,  or 
anything  else  to  make  a  firm  lump,  may  be  used.  (See 
Figs.  1 6  and  35.) 

Bleeding  from  the  Neck.  —  In  studying  the  pulse,  we 
found  the  Carotid  artery  in  the  neck.  If  a  deep  cut  has 
been  made  in  the  upper  part  of  the  neck,  it  might  be  pos- 
sible to  stop  the  flow  by  compressing  the  artery  lower 
down  the  neck. 

3H 


ACCIDENTS.  315 

Wounds  in  the  Thigh.  —  The  femoral  artery  comes 
near  the  surface  in  the  groin.  Pressure  may  be  applied 
here  in  the  same  way  to  stop  bleeding  from  a  cut  farther 
down  the  thigh.  In  the  angle  back  of  the  knee,  pressure 
may  compress  the  artery  supplying  the  leg. 

In  case  of  severe  wounds,  pressure  should  be  applied 
immediately  to  the  wound.  Sometimes  it  is  well  to  make 
a  plug  of  cloth  and  press  upon  the  cut. 

Bleeding  from  Veins.  —  In  case  of  bleeding  from  veins, 
holding  the  part  up  may  check  the  flow.  If  necessary  to 
apply  pressure,  it  should  be  beyond  the  cut,  instead  of 
between  it  and  the  heart,  as  in  the  case  of  the  artery. 

Hemorrhage  of  the  Lungs  or  Stomach.  —  Blood  from 
the  lungs  is  bright,  frothy,  and  salty;  from  the' stomach 
is  dark  and  sour.  In  case  of  bleeding  from  the  lungs  or 
stomach,  let  the  person  rest  quietly  on  a  lounge  or  easy- 
chair.  Give  him  some  bits  of  ice  to  swallow. 

Bleeding  from  the  Nose.  —  Nosebleed  may  sometimes 
be  stopped  by  pressing  firmly  at  the  base  of  the  nose. 
Do  not  lean  forward,  as  this  position  aids  the  flow.  Sit 
up,  and  hold  up  the  head,  and  hold  a  cloth  under  the  nose. 
Apply  cold  water  or  ice  to  the  nose  and  to  the  back  of  the 
neck.  If  this  does  not  stop  it,  inject  cold  water,  with  a 
little  salt  or  soda  in  it,  into  the  nose.  Often  the  flow  may 
be  stopped  by  pressing  firmly  on  the  upper  lip  at  the  sides 
of  the  nose.  If  these  attempts  fail,  a  long  strip  of  cloth 
may  be  used  to  plug  the  nostril,  pushing  the  cloth  in  a 
little  at  a  time,  and  leaving  the  ends  so  it  can  be  pulled 
out.  This  should  not  be  removed  till  a  long  time  after  the 
flow  is  checked,  as  it  may  start  the  bleeding  afresh.  After 
an  attack  of  this  kind  avoid  blowing  the  nose,  as  this  often 
starts  bleeding  again. 


316  PHYSIOLOGY. 

Treatment  of  Burns.  —  Plunge  the  burned  part  into 
cold  water.  As  soon  as  possible  apply  a  solution  of  cook- 
ing soda  (a  tablespoonful  of  bicarbonate  of  soda  to  a  tea- 
cup of  water) ;  or  lay  a  wet  cloth  on  the  burned  part  and 
put  the  soda  on  the  cloth.  Afterwards  apply  vaseline, 
and  renew  the  vaseline  till  the  wound  is  healed. 

A  mixture  of  equal  parts  of  sweet  oil  and  limewater 
makes  a  good  liniment  for  dressing  burns.  Flour  thickly 
applied  gives  relief,  but  is  objectionable  because  it  is  hard 
to  remove  without  taking  the  skin  off  with  it. 

Danger  from  Burning  Clothing.  —  If  the  clothing  takes 
fire,  there  is  added  to  the  danger  of  burning  the  body,  the 
further  risk  of  inhaling  the  flame  and  heated  air.  It  is 
best  to  lie  down  and  roll  or  wrap  the  body  in  any  cloths 
at  hand,  —  rugs,  shawls,  etc.  Running  serves  to  fan  the 
flames.  Hence,  if  a  person  whose  clothing  is  on  fire  is 
seen  to  be  thoroughly  frightened,  and  to  have  lost  presence 
of  mind  and  be  starting  to  run,  the  best  thing  to  do  usually 
is  to  grasp  and  try  to  throw  him  to  the  ground,  putting  a 
wrap  of  some  kind  around  the  body  at  the  same  time  if 
possible.  Rolling  on  the  ground  or  floor  in  itself  would 
very  likely  put  out  a  small  flame. 

Treatment  of  Fainting.  —  Lay  the  body  flat  on  the 
back.  Keep  the  crowd  away,  and  give  plenty  of  fresh  air. 
Loosen  the  clothing  about  the  neck  and  waist.  Sprinkle 
cold  water  on  the  face,  but  do  not  drench  the  body  with  a 
quantity  of  water.  Apply  smelling  salts  (ammonia)  to  the 
nostrils ;  rub  the  limbs  toward  the  body.  If  these  reme- 
dies do  not  soon  restore  consciousness,  send  for  a  physician. 
A  faint  is  not  usually  a  serious  matter.  Bad  ventilation, 
disagreeable  odors,  or  even  the  oversweet  odors  of  such 
flowers  as  the  tuberose,  may  cause  fainting. 


ACCIDENTS.  317 

Broken  Bones.  —  Keep  the  patient  as  quiet  as  possible 
till  the  physician  arrives.  There  need  be  no  anxiety  if  the 
physician  is  delayed,  as  ordinarily  no  harm  comes  from 
waiting.  If  there  is  inflammation,  cold  water  may  be 
applied.  Cooling  applications  are  desirable  in  case  of 
severe  bruises.  If  it  is  necessary  to  carry  the  patient,  lay 
him  on  a  board,  or  at  least  keep  the  injured  part  as  quiet 
as  possible  ;  a  cane  or  umbrella  may  be  tied  alongside  a  leg, 
and  supported  by  a  pillow  or  a  coat.  Sometimes  the  sharp 
ends  of  the  bones  may  cut  the  flesh  or  even  blood  tubes. 

Sunstroke.  —  Lay  the  patient  in  the  shade  and  pour 
cold  water  over  the  head. 


. 


Fig.  96.     Resuscitation  from  Drowning.     (Lincoln,  3  Figures.) 
(Position  1.) 

TREATMENT   OF  THE   DROWNED. 

(As  given  by  the  Michigan  Board  of  Health^) 

RULE  I.    Remove  all  obstructions  to  breathing.     Instantly 
loosen  or  cut  apart  all  neck   and   waist  bands ;  turn  the 


PHYSIOLOGY. 


patient  on  his  face,  with  the  head  down  hill ;  stand  astride 
the  hips  with  your  face  toward  his  head,  and,  locking  your 
fingers  together  under  his  belly,  raise  the  body  as  high  as 
you  can  without  lifting  the  forehead  off  the  ground  (Fig. 
96,  Position  i),  and  give  the  body  a  smart  jerk  to  remove 
mucus  from  the  throat  and  water  from  the  windpipe ;  hold 
the  body  suspended  long  enough  to  count  slowly,  one, 


-   Av^i, 

Fig.  97-     Resuscitation  from  Drowning. 
(Position  2.) 

two,  three,  four,  five,  repeating  the  jerk  more  gently  two 
or  three  times. 

RULE  2.  Place  the  patient  on  the  ground  face  down- 
ward, and,  maintaining  all  the  while  your  position  astride 
the  body,  grasp  the  points  of  the  shoulders  by  the  clothing, 
or,  if  the  body  is  naked,  thrust  your  fingers  into  the  arm- 
pits, clasping  your  thumbs  over  the  points  of  the  shoulders, 
and  raise  the  chest  as  high  as  you  can  (Fig.  97,  Position  2) 


ACCIDENTS. 


319 


without  lifting  the  head  quite  off  the  ground,  and  hold  it 
long  enough  to  count  slowly  one,  two,  three.  Replace 
him  on  the  ground,  with  his  forehead  on  his  flexed  arm,  the 
neck  straightened  out,  and  the  mouth  and  nose  free.  Place 
your  elbows  against  your  knees,  and  your  hands  upon  the 
sides  of  his  chest  (Fig.  98,  Position  3)  over  the  lower  ribs, 
and  press  downward  and  imvard  with  increasing  force  long 


Fig.  98.     Resuscitation  from  Drowning. 
(Position  3.) 

enough  to  count  slowly  one,  two.  Then  suddenly  let  go, 
grasp  the  shoulders  as  before,  and  raise  the  chest  (Position 
2),  then  press  upon  the  ribs,  etc.  (Position  3).  These  al- 
ternate movements  should  be  repeated  ten  or  fifteen  times 
a  minute  for  an  hour  at  least,  unless  breathing  is  restored 
sooner.  Use  the  same  regularity  as  in  natural  breathing. 

RULE  3.    After  breathing  has   commenced,  restore  the 
animal  heat.     Wrap  him  in  warm  blankets,  apply  bottles 


320  J'HYSIOLOGY. 

of  hot  water,  hot  bricks,  or  anything  to  restore  heat.  Warm 
tJic  head  nearly  as  fast  as  tJie  body  lest  convulsions  come  on. 
Rubbing  the  body  with  warm  cloths  or  the  hand,  and  slap- 
ping the  fleshy  parts,  may  assist  to  restore  warmth,  and 
also  the  breathing.  If  the  patient  can  surely  swallow,  give 
hot  coffee,  tea,  milk,  or  a  little  hot  sling.  Give  spirits 
sparingly,  lest  they  produce  depression.  Place  the  patient 
in  a  warm  bed,  and  give  him  plenty  of  fresh  air ;  keep  him 
quiet. 

BEWARE  ! 

Avoid  Delay.  A  moment  may  turn  the  scale  for  life 
or  death.  Dry  ground,  shelter,  warmth,  stimulants,  etc., 
at  this  moment  are  nothing  —  artificial  breathing  is 
everything  —  is  the  one  remedy  —  all  others  are  sec- 
ondary. 

Do  not  stop  to  remove  wet  clothing.  Precious  time  is 
wasted,  and  the  patient  may  be  fatally  chilled  by  the  ex- 
posure of  the  naked  body,  even  in  summer. 

First  restore  Breathing.  —  Give  all  your  attention  and 
effort  to  restore  breathing  by  forcing  air  into,  and  out  of, 
the  lungs.  If  the  breathing  has  just  ceased,  a  smart  slap 
on  the  face  or  a  vigorous  twist  of  the  hair  will  sometimes 
start  it  again,  and  may  be  tried  incidentally. 

Before  natural  breathing  is  fully  restored,  do  not  let  the 
patient  lie  on  his  back  unless  some  person  holds  his  tongue 
forward.  The  tongue  by  falling  backward  may  close  the 
windpipe  and  cause  fatal  choking. 

Prevent  friends  from  crowding  around  the  patient  and 
excluding  the  fresh  air ;  also  from  trying  to  give  stimulants 
before  the  patient  can  swallow.  The  first  causes  suffoca- 
tion ;  the  second,  fatal  choking. 


ACCIDENTS.  321 

Do  not  give  up  too  soon :  you  are  working  for  life. 
Any  time  within  two  hours  you  may  be  on  the  very 
threshold  of  success  without  there  being  any  sign  of  it. 

Learn  to  Swim.  —  Of  course,  persons  who  cannot  swim 
well  ought  not  to  go  out  in  a  boat  without  taking  along 
some  sort  of  a  float  that  may  serve  as  a  life-preserver. 
Some  of  the  rubber  cushions  serve  well  for  this. 

Every  father  neglects  his  duty  if  he  does  not  teach  his 
children,  girls  as  well  as  boys,  to  swim  and  to  float.  One 
cool,  trained  person  may  save  the  lives  of  a  whole  boat 
load. 

When  a  Boat  Upsets.  —  In  case  an  ordinary  rowboat  is 
overturned,  one  should  not  attempt  to  climb  into  it  or  upon 
it.  It  takes  very  little  to  float  a  person  in  water,  as  the 
body  is  only  a  little  heavier  than  water ;  in  fact,  if  a  person 
fills  the  lungs  and  lies  back  in  the  water  his  face  and  nose 
will  keep  above  water,  and  a  person  (at  any  rate  without 
clothing)  can  float  in  this  way  for  some  time  if  he  breathes 
lightly.  The  trouble  is  that  the  person  tries  to  lift  the 
whole  head  out  of  the  water.  The  dog  and  such  animals, 
when  swimming,  have  little  out  of  the  water  but  the  tip  of 
the  nose  and  a  little  of  the  top  of  the  head.  If  we  could 
learn  something  from  them  it  would  be  a  good  thing.  The 
easiest  way  to  float  is  on  the  back.  Few  persons  have 
been  taught  these  facts,  and  most  of  those  who  have 
learned  them  lose  their  presence  of  mind,  and  waste  their 
breath  and  strength  in  wild  and  fruitless  splashing.  If  a 
boat  be  overturned,  those  who  can  swim  should  help  those 
who  cannot  to  get  hold  of  the  edge  of  the  boat,  but  not 
permit  them  to  climb  upon  it.  A  small  plank  will  float  a 
person  if  he  will  not  try  to  lift  much  of  his  body  out  of  the 
water. 


322  PHYSIOLOGY. 

Suffocation  in  Wells.  —  Persons  are  sometimes  suffo- 
cated by  carbon  dioxid  in  wells  and  cisterns.  Before  going 
down  into  a  well,  it  is  a  safe  precaution  to  lower  a  lighted 
candle.  If  this  is  extinguished,  a  warning  is  given.  If  a 
second  person  goes  down  after  one  who  has  become  un- 
conscious, great  care  must  be  taken  that  two  lives  are  not 
lost.  A  rope  should  be  firmly  tied  about  the  body,  a  hook, 
attached  to  another  rope,  taken  to  catch  into  the  clothing 
of  the  first,  and  the  rescuer  should  be  lowered  quickly  and 
brought  up  immediately.  A  small  rope  or  large  cord 
might  be  carried,  by  pulling  which  the  signal  is  given  to 
pull  up. 

In  resuscitating  from  carbon  dioxid  suffocation  use  the 
same  method  as  after  drowning,  except  the  first  part,  which 
is  to  remove  water  from  the  windpipe,  etc. 

Poisons  and  their  Antidotes.  —  Several  of  the  common 
drugs  and  remedies  kept  about  the  house  are  more  or  less 
poisonous.  The  proper  antidote  for  each  should  be  known 
and  kept  at  hand.  In  the  first  place,  all  such  materials 
should  be  kept  locked  up  so  they  will  not  be  taken  by 
children,  or  by  mistake,  as  in  the  haste  of  getting  medicine 
in  the  night.  Again,  all  grown  persons  in  the  family 
should  be  instructed  as  to  the  effects  of  each  poison,  and 
taught  its  antidote.  As  soon  as  any  new  poisonous  drug 
is  bought,  it  should  be  made  a  point  to  read  up  about  it, 
and  procure  an  antidote.  Every  one  should  know  that 
strychnin  causes  spasms,  that  opium  brings  on  stupor, 
with  contracted  pupils,  etc. 

Objects  of  Treatment. — Treatment  aims  at  three  things, 
(i)  to  get  rid  of  the  poison,  (2)  to  neutralize  what  remains 
and  prevent  further  action,  (3)  to  remedy  the  effects  already 
produced. 


ACCIDENTS.  323 

1.  Mustard  a  Common  Emetic.  —  The  most  common 
emetic  is  mustard  ;  a  tablespoonful  in  a  cup  of  warm  water; 
give  half  of  it,  following  with  free  drinking  of  warm  water, 
then  give  the  rest  of  the  mustard.     Do  not  wait  for  it  to 
dissolve,  but  stir  quickly  and  give  at  once.     Provoke  vom- 
iting by  tickling   the  throat  with   a  feather  or  with   the 
finger.     If   the  mouth  of   the  patient  cannot  readily  be 
opened,  insert  the  thumbs  inside  the  cheeks  and  back  of 
the  teeth.     If  mustard  is  not  at  hand,  a  strong  solution  of 
table  salt  will  serve.     In  a  few  cases,  such  as  poisoning  by 
ammonia,  lye,  etc.,  it  is  considered  best  not  to  administer 
an  emetic,  but  to  try  to  neutralize  the  effect. 

2.  Neutralize  the  Poison.  —  To  neutralize  a  poison  this 
general  rule  should  be  known :  an  alkali  may  be  neutral- 
ized by  an  acid,  and  vice  versa.     For  example,  lye  with 
vinegar,  carbolic  acid  with  whiting  or  magnesia,  etc.    Some 
acids  and  alkalis  are  always  about  a  house. 

3.  Give  Something  Soothing.  —  After  any  irritant  poi- 
son some  mild  and  soothing  substance  should  be  given,  — 
white-of-egg,  milk,  mucilage  and  water,  flour  and  water, 
gruel,  olive,  or  castor-oil.     These  materials  are  partly  for 
neutralizing   the    poison,  and   are   also    soothing  in   their 
effect.     If  a  patient   is  drowsy,  some   stimulant  may  be 
given,  as  strong  coffee  (after  opium).     Of  course  a  physi- 
cian should  be  sent  for  immediately,  as  the  after-treatment 
is  of  great  importance. 

The  tables  of  "  Poisons,  their  Symptoms,  Antidotes,  and 
Treatment,"  in  the  appendix,  are  taken  from  the  excellent 
Text-Book  of  Nursing  by  Clara  Weeks-Shaw. 

Wounds  from  Thorns,  Rusty  Nails.  —  Promote  bleed- 
ing by  rubbing  and  pressing  the  wound  and  bathing  with 


324 

warm  water.     Or  suck  the  wound.     This  tends  to  remove 
any  injurious  matter.     Apply  poultices. 

Bites  of  Cats,  Bogs,  etc.  —  If  the  animal  is  rabid  (mad), 
suck  the  wound  and  cauterize  quickly.  A  poker  or  nail 
heated  red  hot  is  best  for  cauterizing.  If  one  cannot  do 
this  promptly,  get  lunar  caustic  with  which  to  cauterize ; 
strong  acid  or  alkali,  or  a  coal  of  fire,  may  be  applied  at 
once  to  the  wound  ;  the  coal  on  a  cigar  may  be  used.  Do 
not  kill  the  animal  if  there  is  doubt.  Keep  it  confined, 
and  if  it  proves  a  false  alarm  much  anxiety  will  be  saved. 

Snake  Bites.  —  Apply  ligatures  around  the  part  between 
it  and  the  heart.  Suck  the  wound  (there  is  no  danger 
in  this  if  there  are  no  sores  or  cracks  in  the  skin  of  the 
mouth ;  venom  is  not  a  stomach  poison,  though,  of  course, 
it  should  not  be  swallowed).  Then  apply  caustics,  or  a 
live  coal.  Have  the  patient  drink  freely  of  whiskey  or 
brandy.  If  ammonia  water  is  at  hand,  add  five  teaspoon- 
fuls  to  each  pint  of  liquor. 

Ammonium  carbonate,  ten  per  cent  solution,  is  also 
highly  recommended.  A  teaspoonful  dose  should  be 
given  immediately,  and  repeated  twice  at  intervals  of  ten 
minutes. 

Bee  Stings.  —  Apply  soda,  or  dilute  ammonia. 

Poison  Ivy. — The  itching  and  discomfort  may  be 
relieved  by  bathing  the  part  in  a  mixture  of- 

Two  teaspoons  of  carbolic  acid  (pure), 

Two  tablespoons  of  glycerin, 

One  half  pint  of  water  or  rose-water. 

The  Sick-room.  —  Every  boy  and  girl  ought  to  learn 
something  about  the  care  of  the  sick,  as  any  one  is 
likely  to  be  called  on  to  do  this  kind  of  work.  Good 


ACCIDENTS.  325 

nursing  is  often  "half  the  battle."  In  the  first  place, 
the  nurse  should  faithfully  follow  the  directions  of  the 
physician.  This  obedience  should  be  complete  as  to  admis- 
sion of  visitors,  as  well  as  in  administering  medicine,  etc. 
The  nurse  often  yields  to  the  persuasion  of  some  unwise 
friend,  "  It  won't  do  any  harm  for  him  to  see  me." 

Qualities  of  a  Nurse.  —  The  nurse  should  have  a  quick 
sympathy,  and  make  the  patient  feel  that  all  that  can  be 
done  for  his  comfort  will  be  done ;  yet  this  sympathy  must 
not  lead  the  nurse  to  do  anything  for,  or  give  anything  to 
the  patient  contrary  to  the  orders  of  the  physician.  The 
nurse  should  always  be  cheerful,  even  when  the  patient 
is  "impatient"  and  annoying  in  his  demands.  The 
patient  is  not  "himself,"  and  no  attention  should  be  paid 
to  his  unnatural  irritability. 

The  Room  should  be  Cheery.  —  The  patient  should 
have  a  cheerful  room,  but  the  bed  should  be  so  placed 
that  the  light  will  come  not  too  strongly  into  his  face. 
Evidence  of  illness,  such  as  medicine  bottles,  etc.,  should 
be  kept  out  of  sight  so  far  as  possible. 

Hope.  —  While  it  is  not  best  to  deceive  the  patient  as 
to  his  condition,  there  should  at  all  times  be  kept  up 
an  air  of  cheerfulness  and  hope.  If  the  physician  can 
inspire  with  confidence,  and  the  nurse  give  unflagging 
good  cheer,  the  chances  of  recovery  are  vastly  improved. 
Nothing  sustains  like  hope. 

Pure  Air  in  the  Sick-room.  —  Keep  the  air  of  the  room 
pure.  Remove  excreta  and  everything  offensive  just  as 
soon  as  possible.  Do  not  rely  on  feeling  as  to  tempera- 
ture, but  keep  a  thermometer  in  the  room. 

Sympathy  with  the  Patient.  —  One  of  the  necessary 
characteristics  of  a  good  nurse  is  the  power  of  imagina- 


326  PHYSIOLOGY. 

tion.  "  How  would  I  feel,  and  what  would  I  like  to  have 
done  for  me,  if  I  were  in  his  place  ? "  This  feeling  will 
lead  the  nurse  frequently  to  raise  the  patient's  head  and 
turn  the  pillow  —  the  coolness  of  the  other  side  of  the 
pillow  is  refreshing ;  to  give  sips  of  cool  water ;  to  see 
that  the  patient  does  not  surfer  for  want  of  a  bath  ;  in 
giving  a  bath,  to  do  the  work  thoroughly,  as  a  skillful 
barber  carefully  and  thoroughly  reaches  every  fold  and 
crevice  back  of  the  ear,  etc. 

Bathing  the  Sick.  — In  bathing  a  weak  person  only  a 
part  of  the  body  should  be  moistened  at  a  time ;  after  this 
part  is  thoroughly  dried,  another  part  may  be  washed  ; 
it  is  often  necessary  to  do  all  this  work  under  the  bed 
clothing. 

Changing  the  Bedding.  —  In  changing  the  bed  clothing 
move  the  patient  to  one  side  of  the  bed,  push  the  cloth- 
ing along  close  to  his  body,  and  place  the  clean  bedding 
on  the  other  side ;  then  move  the  patient  back,  remove 
the  soiled  linen,  and  smooth  out  the  clean.  It  is  often 
necessary  to  warm  the  sheets  first :  they  should  be  thor- 
oughly dry. 

Follow  Physician's  Directions  Faithfully.  -  -  Have 
the  physician's  directions  written  out  plainly,  as  they  may 
be  forgotten  ;  and  if  there  is  a  change  of  nurses  during 
the  night  there  is  less  chance  of  mistake.  Never  let  your- 
self get  drowsy  when  acting  as  nurse.  Get  up  and  walk 
about,  get  a  breath  of  fresh  air,  and  if  inclined  to  be 
drowsy  do  not  allow  yourself  to  settle  back  in  an  easy- 
chair.  If  watching  all  night,  take  a  good  lunch  in  the 
middle  of  the  night ;  coffee  may  help  to  keep  you  awake. 
It  is  not  to  be  expected  that  one  who  has  worked  hard 
all  day  out-doors  will  be  likely  to  keep  awake  all  night. 


ACCf DENTS.  327 

There  should  be  day  and  night  watchers,  and  one  wo.uld 
better  not  watch  more  than  six  hours  at  a  time. 

Sweeping  the  Sick-room.  —  Do  not  allow  the  room  to 
be  swept  with  the  ordinary  broom.  The  room  should  have 
rugs  that  can  be  removed  and  shaken,  and  the  floor  wiped 
with  a  moist  cloth.  If  the  room  is  carpeted,  it  may  be 
swept  with  moist  salt,  tea-grounds  or  coffee-grounds,  saw- 
dust, etc.  Any  dusting  should  be  avoided  ;  furniture  may 
be  wiped  with  a  damp  cloth. 

Do  not  Whisper.  —  In  the  effort  to  be  quiet  many  make 
a  mistake  ;  do  not  whisper,  as  it  disturbs  more  than  talking, 
and  also  has  an  air  of  secrecy  that  rouses  suspicion  in  the 
patient. 

Walk  Flat-footed.  —  In  walking  on  tiptoe  often  floors 
and  stairs  are  made  to  creak  when  they  would  not  in  ordi- 
nary circumstances.  It  takes  little  reflection  to  see  that 
in  walking  on  tiptoe  one  brings  more  weight  than  usual 
on  a  smaller  part  of  the  floor,  and  is  therefore  more  likely 
to  spring  a  board  in  the  floor ;  it  is  best  to  walk  flat-footed. 
Wear  an  easy  pair  of  shoes ;  an  old  pair  are  likely  to  be 
quiet. 

Food  for  the  Sick.  —  Raise  the  head  with  the  hand,  or 
bolster  the  patient  up,  when  giving  drink  ;  or  if  the  patient 
is  very  weak,  use  a  rubber  tube,  so  that  he  will  not  have  to 
lift  the  head.  The  nurse  should  know  how  to  prepare  any 
food  that  may  be  needed  during  the  night.  An  oil  stove 
or  gas  stove  is  very  desirable  for  cooking,  or  heating  poul- 
tices, as  an  ordinary  wood  or  coal  fire  is  likely  to  die  down, 
making  it  impossible  for  the  nurse  to  do  this  work  quickly, 
as  is  often  necessary  to  take  advantage  of  a  favorable 
time,  as  when  the  patient  wakens. 


328  PHYSIOLOGY. 

Care  of  Lamps.  —  Most  lamps,  when  turned  low,  give 
off  a  disagreeable  gas.  It  is  better  to  have  a  very  small 
lamp  burning  at  full  height  than  a  large  one  turned  low  ; 
sperm  candles  are  recommended. 

Bandaging,  Preparing  Food,  etc.  —  It  is  well  for  every 
one  to  know  something  about  bandaging,  preparation  of 
food  for  the  sick,  etc.  Space  here  will  not  allow  further 
treatment  of  these  subjects,  and  the  student  is  referred  to 
treatises  on  the  care  of  the  sick,  of  which  there  are  several 
good  ones  mentioned  at  the  end  of  this  chapter. 

To  Prevent  Sneezing.  —  It  is  well  known  that  a  sneeze 
may  be  prevented  by  firmly  pressing  on  the  upper  lip. 
This  may  enable  a  nurse  to  keep  from  waking  a  very  sick 
patient  when,  at  a  critical  point,  sleep  is  almost  a  question 
of  life  or  death.  And  it  is  a  convenient  fact  for  any  one 
to  know.  To  prevent  coughing  there  are  cough  drops  that 
will  relieve  the  tickling  in  the  throat. 

For  Disinfectants  see  Appendix. 

In  addition  to  the  list  of  books  on  Accidents,  Emer- 
gencies, etc.,  already  given,  read  Hand-Book  of  Nursing, 
published  under  the  direction  of  the  Connecticut  Training- 
School  for  Nurses,  State  Hospital,  New  Haven,  Conn. ; 
Text-Book  of  Nursing,  Weeks-Shaw;  Nursing:  Its  Prin- 
ciples and  Practice,  Hampton. 


Summary.  —  i .   To  stop  flow  of  blood  from  an  artery  apply  pres- 
sure to  the  wound,  or  between  the  wound  and  the  heart. 

2.  To  stop  flow  of  blood  from  a  vein  apply  pressure  to  the  wound  or 
beyond  the  heart. 

3.  Leaning  forward  promotes,  instead  of  checking,  nosebleed. 

4.  To  burns  apply  cooking  soda. 

5.  If  the  clothing  takes  fire  lie  down  and  roll,  or  wrap  a  nig  or  shawl 
about  the  body. 


ACCIDENTS.  329 

6.  If  a  person  with  clothing  on  fire  loses  his  presence  of  mind,  seize, 
throw  down,  and  wrap  in  any  woolen  clothing. 

7.  In  case  of  fainting  lay  the  body  flat  on  the  back,  loosen  clothing, 
give  fresh  air,  and  sprinkle  lightly  with  cold  water ;  if  this  does  not 
revive,  rub  the  limbs  toward  the  body,  hold  to  the  nostrils  smelling- 
salts  (or  ammonia)  and,  last,  send  for  a  physician. 

8.  Broken   bones  do  not  urgently   need  prompt  attention.     Keep 
patient  quiet  and  send  for  a  physician. 

9.  For    resuscitation    from     drowning,    use    artificial    respiration, 
promptly  begun  and  long  continued. 

10.  Before  going  down  into  a  well,  test  the  air  by  lowering  a  lighted 
candle. 

1 1 .  Learn  the  antidotes  of  every  poison  in  your  house  as  soon  as  it  is 
bought,  and  keep  the  antidote  at  hand. 

12.  Volunteer  to  help  take  care  of  sick  friends,  and  learn  to  do  this 
work  well. 

Questions.  —  i.    How   does   holding  up   the  wounded   part   check- 
bleeding  ? 

2.  What   other    methods   of   resuscitation   from   drowning  are   in 
use? 

3.  What  are  some  of  the  poisonous  substances  commonly  kept  in 
the  house? 


CHAPTER   XXIV. 
THE   SKELETON. 

The  Two  Parts  of  a  Skeleton.  —  Observe  that  the 
skeleton  as  a  whole  consists  of  two  portions,  the  axial  por- 
tion, consisting  of  a  central  axis,  the  spinal  column,  to 
which  the  head  belongs ;  and  the  appendicular  portion, 
the  limbs  and  the  bones  belonging  to  them. 

The  Uses  of  the  Bones.  —  In  the  skeleton  as  a  whole 
observe  :  — 

1.  The  skeleton  shows  the  form  of  the  body. 

2.  It  supports  the  softer  tissues. 

3.  It  protects  softer  parts,  as  the  brain  in  the  skull,  the 
spinal  cord  in  the  spinal  column,  the  heart  and  lungs  in 
the  thorax,  etc. 

4.  The  bones  serve  as  levers  in  producing  motion  and 
locomotion. 

Study  of  a  Vertebra.  —  Take  a  vertebra  from  the  middle  of  the 
spinal  column  :  — 

1.  Its  most  solid  part  is  its  body,  or  centrum. 

2.  On  the  dorsal  side  of  this  is  the  neural  arch,  forming  with  the 
body  the  neural  ring,  through  which  the  spinal  cord  passed. 

3.  From  this  arch  there  extend  projections,  or  processes.     Hold  the 
vertebra  by  the  tip  of  its  longest  process,  and  place  it  beside  the  cor- 
responding vertebra  in  the  complete  skeleton.     Note  that :  — 

(rt)  The  body  is  flattened  where  it  fitted  against  the  vertebras 
anterior  and  posterior  to  it ; 

(b)    The  holes  in  the  vertebrae  form  a  passage  for  the  spinal  cord; 

330 


THE  SKELETON. 


331 


(V)    The  middle  process  is  the  spinous  process,  and  the  series  of 
spinous  processes  form  the  ridge  of  the  backbone ; 

(d)   The  two  lateral  processes  are  the  transverse  processes. 


Neural   Arch 


Body. 


Transverse  Process 


Spinous  Process 


Neural  Ring 
Fig.  99-    Anterior  View  of  Thoracic  Vertebra. 

Demi-Facet  for  Head  of  Rib 


Body 


Anterior  Articular 

Process 


....  Facet  for  Tubercle 
of  Rib 


"•Transverse  Process 


—  Spinous  Process 


Fig.   100.     Left  Side  View  of  Thoracic  Vertebra. 

Fit  together  two  vertebrae  in  their  proper  order  and  observe  that :  — 
(e)    The  openings  at  the  sides,  through   which   the  spinal  nerves 
passed,  are  formed  by  adjacent  notches,  or  grooves,  in  the  contiguous 
vertebrae. 

(/)  The  two  projections  extending  anteriorly  from  the  ring  of  one 
vertebra  fit  against  two  corresponding  processes  extending  posteriorly 
from  the  other  vertebra.  These  are  the  anterior  and  posterior  articu- 
lating processes. 


332 


PHYSIOLOGY. 


Temporal 


Frontal 


Phalanges 

\       Carpus 


Metacarpus     Ulna     Sternum 


.... .  Parietal 

Occipital 

Cervical  Vertebrae 


i Tnoracic  Vertebrae 


Fumbar  Vertebrae 


Sacrum 

Coccyx 


Femur 


Fibula 


Tarsus 


Phalanges.. 


Metatarsus 
Fig.   101.     Side  View  of  the  Human  Skeleton. 


THE  SKELETON. 


333 


TABLE  OF  THE   BONES. 


r  skuii  (8) 


HEAD  (28)  • 


Face  (14) 


1  Ears  (6) 

CERVICAL  REGION  (8) 
THORAX  (37 


UPPER  EXTREMITIES  (64)   {  Arm. 


Frontal  (forehead). 

2  Temporal  (temples) . 

2  Parietal  (side). 
"i  Occipital  (posterior  base). 
|  Sphenoid  (base). 
[  Ethmoid  (base  of  nose  and  between  eyes). 

f  2  Superior  Maxillae  (upper  jaw). 

2  Nasal  (bridge  of  nose). 

2  Malar  (cheek). 

2  Lacrymal  (inner  front  corner  of  orbit). 

2  Turbinated  (within  nostrils). 

2  Palate  (posterior  hard  palate). 

Vomer  (nasal  partition). 
(  Inferior  Maxilla  (lower  jaw). 

(  Malleus  (hammer). 
{  Stapes  (stirrup). 
I  Incus  (anvil). 

\  7  Cervical  Vertebrae  (neck). 
|  Hyoid  Bone  (base  of  tongue). 

(  14  True,  6  False,  4  Floating  Ribs. 
-1   12  Thoracic  Vertebrae  (back). 
I  Sternum. 


\  Clavicle  (collar-bone). 
^  Scapuk  (shoulder.blade)i 

(  Humerus  (arm). 


Hand. 


f8' 

51 
I  14 


8  Carpal  (wrist). 
Metacarpal  (palm). 
Phalanges  (fingers). 


LUMBAR  REGION  (5) 
PELVIS  (4) 

LOWER  EXTREMITIES  (60) 


5  Lumbar  Vertebrae  (loins). 


(  2  Innominate. 

\  Sacrum. 
I  Coccyx. 


Thigh. 

Leg. 


Femur. 

f  Patella  (knee-pan). 
i  Tibia  (large  bone). 
I  Fibula  (outer  bone). 
C  7  Tarsal  (instep,  heel) 
-]  5  Metatarsal  (arch). 
I  14  Phalanges  (toes). 


334 


PHYSIOLOGY. 


The  Spinal  Column.  —  The  central  part  of  the  skeleton 
is  the  backbone,  or  spinal  column.  As  a  whole  it  is  a 
column,  widening  toward  the  base,  composed  of  a  series  of 
separate  bones  called  vertebrae. 


Hole  for  Blond  Tubes 


Body 


Anterior  Articular  Facet 

..Neural  Arch 


Spinous  Process 


'"•-»  Neural  Ring 


Fig.  102.    Anterior  View  of  Cervical  Vertebra. 


Body--- 


Spinous  Process 


Fig.  103.    Left  Side  View  of  Cervical  Vertebra. 

Each  vertebra  has  seven  processes,  four  articulating 
(two  anterior  and  two  posterior),  two  transverse,  and  one 
spinous. 

Take  a  thoracic  vertebra  and  in  the  presence  of  the  class  trim  off  the 
processes  with  a  pair  of  bone-forceps.  The  vertebra  will  he  seen  to  be 
essentially  a  ring,  or  padlock,  consisting  of  the  body  and  neural  ring  or 
arch. 


THE  SKELETON.  335 

Articulations  of  a  Vertebra. —  The  smooth  places  where 
the  articulating  processes  join  are  called  facets.  Observe 
on  each  side  of  the  body  of  the  vertebra  a  facet  where  the 
head  of  the  rib  articulated.  There  is  also  a  facet  on  the 
transverse  process  where  the  tubercle  of  the  rib  articulated. 

The  Cervical  Vertebrae.  —  The  seven  cervical  vertebrae 
(neck)  have  holes  through  their  sides,  or  transverse  pro- 
cesses, for  the  passage  of  blood  tubes. 

Atlas  and  Axis.  —  The  first  vertebra,  the  atlas,  has  no 
body.  The  second  vertebra  is  the  axis.  It  has  a  peg, 
called  the  odontoid  process,  which  represents  the  body  of 
the  atlas.  In  shaking  the  head,  the  atlas,  with  the  head, 
turns  on  the  axis.  In  nodding  the  head,  the  head  simply 
rocks  back  and  forth  on  the  atlas. 

The  Thoracic  Vertebrae.  —  The  twelve  rib-supporting 
vertebrae  are  the  thoracic  vertebrae. 

The  Lumbar  Vertebrae.  —  The  next  five  are  the  lumbar. 

The  Sacrum  and  Coccyx.  —  The  sacrum  is  composed  of 
five  vertebrae  grown  together,  and  the  remaining  four  are 
combined  in  the  coccyx. 

Review  of  the  Spinal  Column.  —  Let  the  eye  slowly 
review  the  whole  spinal  column,  noting  what  the  vertebrae 
have  in  common.  Note  also  their  differences. 

Flexibility  of  the  Spinal  Column.  —  In  most  articulated 
skeletons  there  are  pads  of  felt  between  the  vertebrae. 
These  take  the  place  of  the  inter-vertebral  cartilages, 
which  are  a  form  of  connective  tissue,  possessing  the  elas- 
ticity of  cartilage  and  the  toughness  of  fibrous  connective 
tissue,  such  as  ligament  and  tendon.  These  inter-vertebral 


336 


PHYSIOLOGY. 


cartilages  serve  both  to  keep  the  vertebrae  apart  and  to 
hold  them  together.  When  we  bend  the  shoulders  to  the 
right,  the  right  edges  of  these  cartilages  are  compressed, 


Neural  Arch 


Transverse  Process 


Body-  — 


Neural   Ring 
Fig.  104.    Anterior  View  of  Lumbar  Vertebra. 


Body 


-  Spinous 
Process 


Posterior  Articular  Process 
Fig.  105.    .Side  View  of  Lumbar  Vertebra. 

and  the  left  edges  are  stretched,  as  a  piece  of  india  rubber 
would  be  if  it  were  glued  between  the  ends  of  two  spools, 
and  the  whole  were  slightly  bent. 

Curves  of  the  Spinal  Column.  —  View  the  spinal  column 
from  the  side.     Draw  a  line  representing  all  its  curves. 


THE  SKELETON.  337 

The  Cavities  of  the  Skeleton.  —  Examine  the  cavity  o/~  the  skull. 
If  the  class  has  not  a  skull  which  has  been  sawed  across,  look  into  the 
skull  cavity  through  the  hole  where  the  spinal  cord  joined  the  brain. 

Observe  the  conical  shape  of  the  thorax.  In  the  entire  body  the 
bones  and  muscles  about  the  shoulders  usually  make  a  reversed  cone  of 
the  upper  part  of  the  trunk. 

Observe  that  the  ribs  are  connected  with  the  breastbone  by  carti- 
lages. 

The  upper  limbs  are  articulated  with  the  body  only  where  the  inner 
ends  of  the  collar  bones  join  the  breastbone. 

Pronation  and  Supination.  —  Rest  the  forearm  on  the  table  with  the 
palm  up ;  keeping  the  elbow  fixed,  turn  the  hand  over.  Turning  the 
palm  up  is  called  supination  ;  turning  it  down  is  pronation.  Perform 
this  experiment  with  the  articulated  skeleton. 

The  Skeleton  of  a  Cat  or  Rabbit.  —  Examine  the  skeleton  of  a  cat 
or  rabbit  for  the  sake  of  comparison.  Note  especially  the  skull  and 
spinal  column,  so  that  you  will  know  better  what  to  do  when  dissecting 
the  brain  and  spinal  cord  in  one  of  these  animals. 

The  Weight  of  Bones.  —  The  bones  make  about  one  sixth 
of  the  weight  of  the  living  body.  When  dried  they  may 
lose  half  of  their  weight. 

Microscopic  Structure  of  Bone,  i .  Examine  with  a  hand  lens.  — 
Hold  a  mounted  cross-section  of  bone  up  to  the  light  and  examine  with 
a  hand  lens.  The  solid  part  of  the  bone  will  be  seen  to  be  pierced  by 
many  small  holes  (or  if  the  holes  are  filled  they  will  appear  as  black 
spots).  These  are  the  cross-sections  of  the  haversian  canals,  through 
which  run  the  blood  tubes,  mainly  lengthwise  through  the  bone. 

2.  Examine  with  the  Low  Power  of  a  Compound  Microscope.— 
Examine  the  section  under  the  microscope,  using  a  half-inch  objective. 
The  bony  matter  will  now  be  seen  to  be  arranged  in  circles,  lamellae, 
around  the  haversian  canals,  somewhat  like  the  rings  seen  on  the  end 
of  a  log. 

Between  the  rings  are  circles  of  elongated  dark  dots.  These  are 
lacunae,  cavities  in  which  lay  the  live-bone  corpuscles  which  built  up 
the  bone.  The  bone  was,  at  first,  cartilage.  Later,  mineral  matter 
was  deposited,  forming  true  bone. 


33* 


PHYSIOLOGY. 


3.  Examine  with  a  High  Power. —  Now  examine  the  section 
under  a  one-fifth-inch  objective.  From  the  lacunae  there  run  out,  in 
every  direction,  little  crevices,  appearing  as  fine  black  lines.  These 
are  the  canaliculi.  Through  the  haversian  canals,  lacunae,  and  cana- 
liculi,  the  nourishing  materials  of  the  blood  reach  all  parts  of  the  bone. 

The  Chemical  Composition  of  Bone.  —  i .  Take  a  tall,  narrow 
glass  jar,  called  in  the  chemical  laboratory  a  "graduate,'1  or  a  lamp 
chimney  corked  at  one  end  answers  very  well,  and  nearly  fill  with 

Lamellae  Lacunae 


\ 

Canaliculi  Haversian  Canal 

Fig.  106.    Cross-section  of  Bone.    (Highly  Magnified.1) 

water.  Add  one  sixth  as  much  hydrochloric  acid.  Put  into  this  a 
slender,  dry  bone,  such  as  a  fibula  or  rib.  In  twenty-four  hours  take  it 
out,  rinse  it  thoroughly,  and  examine  it.  The  acid  will  probably  have 
dissolved  out  the  mineral  matter  and  left  the  animal  matter. 

2.  Lay  a  piece  of  bone  on  a  shovel,  or  piece  of  sheet  iron,  and  place 
in  the  fire.  The  animal  matter  is  burned  out,  leaving  the  brittle  min- 
eral matter. 


THE  SKELETON.  339 

Bone  is  composed  of  mineral  matter,  two  thirds,  and  animal  matter, 
one  third  ;  in  childhood  the  animal  matter  is  in  larger  proportion,  while 
in  old  age  the  mineral  matter  is  in  excess. 

The  mineral  matter  is  chiefly  calcium  phosphate,  while  the  animal 
matter  is  largely  gelatin. 

Joints  may  be  classified  according  to  their  structure  as 
follows :  — 

Classification  of  Joints.  —  i.  Immovable,  such  as  the 
sutures  between  the  bones  of  the  skull ; 

2.  Mixed,  such  as  the  joints  between  the  vertebrae ; 

3.  Movable,  which  allow  free  motion  between  the  parts  ; 
(a}  Ball  and  socket,  as  in  the  hip  and  shoulder ; 

(b)  Hinge,  as  in  the  knee  and  elbow ; 

(c)  Pivot,  as  in  the  forearm,  and  between  the  atlas  and 
axis ; 

(d)  Gliding,  as  between  the  short  bones  of  the  wrist,  and 
of  the  ankle. 

Study  of  Joints.  —  Examine  these  joints  in  the  articulated  skeleton, 
and  so  far  as  possible,  in  fresh  specimens  (of  rabbits).  Compare  the 
ball  and  socket  joints  of  the  hip  and  shoulder.  Also  compare  the  hinge 
joints  of  the  knee  and  elbow. 

Hygiene  of  the  Bones.  —  Sometimes  the  bones  of  chil- 
dren are  deficient  in  mineral  elements,  and  are  unduly  soft 
and  flexible.  This  condition  indicates  a  disease  called 
rickets.  Even  if  the  bones  are  normal,  children  should 
not  be  encouraged  to  walk  early,  as  bow-legs  may  result. 
Most  bow-legged  persons  seem  to  be  active,  and  probably 
their  muscles  developed  faster  than  the  bones.  Constrained 
positions  or  excessive  use  of  special  groups  of  muscles  may 
result  in  lateral  curvature  of  the  spine.  The  height  of 
seats  and  desks  should  be  carefully  looked  after. 

Sprains  and  Dislocations.  —  Sprains  and  dislocations 
are  injuries  to  the  joints,  and  often  bring  more  serious 


340  PHYSIOLOGY. 

results  than  a  broken  bone.  There  should,  usually,  be 
complete  rest  until  the  part  can  be  used  without  pain. 
Otherwise  a  stiffened  joint  may  result.  Hot  water  applied 
to  a  sprain  or  bruise  promotes  circulation  and  prevents  dis- 
coloration. But  if  there  is  inflammation  cold  water  should 
be  applied.  Bandages  may  be  needed  for  support. 


Summary.  —  i .  The  skeleton  consists  of  the  axial  and  appendicular 
portions. 

2.  Each  vertebra  consists  of  a  body,  ring  (around  spinal  cord)  and 
processes. 

3.  Pads  of  cartilage  connect  the  vertebrae. 

4.  Bone  is  traversed  by  tubes  and  crevices  through  which  it  receives 
its  nourishment  from  the  blood. 

5.  Bone  consists  of  animal  matter  with  limy  matter  embedded  in  it. 

6.  Sprains  should  be  treated  carefully  to  avoid  stiffened  joints. 

Questions. —  i.   Why  do  the  bones  of  old  people  break  so  much 
more  easily  than  those  of  children  ? 

2.  What  is  the  use  of  the  central  marrow? 

3.  What  is  the  work  of  the  red  marrow  in  the  spongy  ends  of  the 
bones  ? 

4.  What  are  "  sesamoid  "  bones  ? 


CHAPTER    XXV. 
THE  MUSCLES. 

The  Number  of  Muscles.  —  There  are  over  five  hun- 
dred muscles  in  the  human  body.  These  vary  in  size  from 
less  than  an  inch  in  length,  in  the  ear  and  in  the  larynx, 
to  a  foot  and  a  half  long  in  the  thigh. 

The  Arrangement  of  Muscles.  —  The  muscles  of  the 
two  sides  of  the  body  are  paired,  and  normally  are  about 
equal  in  size  and  strength.  The  muscles  of  the  limbs  are 
further  paired  into  flexors,  which  bend,  and  the  extensors, 
which  straighten  the  limbs.  The  muscles  are  also  arranged 
more  or  less  in  layers.  There  is  generally  a  superficial 
layer  and  a  more  deep-seated  layer. 

Forms  of  Muscles.  —  Muscles  are  of  various  shapes. 
The  prevailing  form  in  the  limbs  is  spindle-shaped,  or  fusi- 
form. This  is  convenient,  as  the  thicker  middle  portion 
of  the  muscle  is  opposite  the  more  slender  part  of  the 
bone,  while  the  tendons  at  the  ends  of  the  muscles  are 
opposite  the  enlarged  ends  of  the  bones  at  the  joints. 
Some  muscles  are  flat,  some  have  their  fibers  arranged 
like  the  barbs  of  a  feather,  and  are  hence  called  penni- 
form.  Some  muscles  have  a  tendon  in  the  middle  which 
runs  through  a  loop,  as  in  the  case  of  the  muscle  which 
depresses  the  lower  jaw.  As  already  stated,  muscles 
which  close  openings  are  circular,  and  are  called  sphincter 
muscles. 

34' 


342 


PHYSIOLOGY. 


Deltoid 


Serratus  Magnus 


Rectus  Femoris 


Tibialis  Anticu: 


Extensors  of  the  Hand 
Flexors  of  the  Hand 


Pectoralis  Major 


Rectus  Abdominalis 


....    Sartorius 


Vastus  Externus 


Extensors  of  the  Toes 


Fig.   107.    Ventral  View  of  the  Superficial  Muscles 


THE  MUSCLES. 


343 


Extensors  of  the  Hand 


Triceps 


Latissimus  Dors 


Gluteus   Maximus 


Vastus  Externus 


Flexors  of  the  Foot  — 


Trapezius 


Deltoid 


--  Flexors  of  the  Hand 


•Biceps  Cruris 


Gastrocnemius 


Tendo  Achillis 


Fig.   108.    Dorsal  View  of  the  Superficial  Muscles. 


344 


PHYSIOLOGY. 


Names  of  Muscles.  —  Some  muscles  are  named  from 
their  shape,  as  the  deltoid  on  the  shoulder ;  from  position, 
pectoralis  major ;  from  their  supposed  action,  as  sartorius 
and  adductor ;  direction,  as  rectus,  etc.  The  biceps  and 
triceps  are  named  from  their  division  at  their  origins. 

Peculiar  Muscles.  —  The  diaphragm  is  a  sheet  of  muscle 
that  forms  a  partition  between  the  chest  and  the  abdomen. 
It  is  arched,  and  has  a  clear  tendinous  center.  The  ab- 
dominal muscles  form  a  wall  to  hold  the  organs  of  the 
abdominal  cavity.  These  muscles  also  aid  in  breathing, 
especially  in  forced  expiration,  as  after  violent  exercise 
and  in  coughing.  The  abdominal  wall  consists  of  several 

layers  of  muscle. 

Heart  Muscle.  —  The  fibers 
which  make  up  heart  muscle 
are  different  in  appearance  from 
either  the  striated  or  smooth 
muscle  fibers.  They  are  more 
or  less  branched,  as  shown  in 
the  accompanying  figure.  No 
sheath  has  been  found  on  these 
fibers. 

The  Three  Kinds  of  Muscular 
Fibers  Compared.  —  For  the 
sake  of  comparison,  the  striated 
and  unstriated  muscle  fibers  are 
here  shown  again,  alongside  the 
tschweigger-seideu  heart  muscle  fibers.  The  stri- 

The  nuclei  and  cell-junctions  are  only 
represented  on  the  right  hand  side    ated    fibers  (of   the   skeleton)  are 

usually  called  "voluntary,"  and 

the  plain  fibers  "involuntary."     The  heart  muscle  fibers 
are  intermediate,  being  striated,  but  involuntary  in  their 


THE  MUSCLES. 


345 


action.  A  striated  muscle  fiber  may  be  i|  inches  long  and 
•2-g-0-  of  an  inch  wide,  though  usually  less.  The  heart  muscle 
fiber  is  narrower  than  the  skeletal  fiber,  and  the  plain  fiber 
very  much  smaller  than  either.  (But  the  figures  do  not 
attempt  to  give  relative  proportions  with  any  exactness.) 

Each  Muscle  Fiber  is  a  Muscle  Cell.  —  It  is  easily  seen 
that  each  plain  muscle  fiber  is  a  single  cell,  having  its  dis- 
tinct nucleus.  The  same  is  true  of  the  heart  muscle  fibers, 


Nucleus 


pv.-"»-    Isolated  Fiber 


•-  Fibers  Joined 


Fig.   110.  —  Plain  (unstriated)   mus- 
cular fibers  from  the  bladder. 


Fig.  1 1  1.  — Two  striated  mus- 
cular fibers  showing  the  ter- 
minations of  the  nerves. 


though  they  are  not  so  simple,  being  more  or  less  branched. 
In  the  development  of  striated  muscle,  when  the  muscular 
fibers  are  about  to  be  formed,  the  cells  from  which  they 
develop  (called  muscle  plates)  become  elongated  so  that 
each  cell  is  converted  into  a  long  protoplasmic  fiber,  with 
many  nuclei.  Most  investigators  agree  that  the  striated 
fibers  are  produced  by  the  elongation  of  single  cells  with 
multiplication  of  their  nuclei,  though  some  have  thought 
that  the  fiber  is  formed  by  the  coalescence  of  several  cells 
end  to  end. 

Muscles  of  Expression.  —  The  facial  expression  is  due 
to  the  action  of  the  muscles  of  the  face,  which  in  turn  are 


340  PHYSIOLOGY. 

under  control  of  the  cranial  nerves.  The  habitual  position 
becomes  somewhat  "  fixed,"  so  it  is  true  that  character 
is  often  shown  by  "  the  looks."  Cultivation  of  happy 
thoughts  therefore  tends  to  make  one  better  looking. 

Muscles  and  Fat.  —  Fat  fills  in  space  between  muscles, 
and,  if  abundant,  forms  a  layer  over  the  muscles.  One 
notable  instance  is  the  hollow  triangular  space  between 
the  muscles  of  the  cheek.  If  there  is  very  little  fat,  a 
depression  is  seen,  forming  the  "hollow  cheeks.''  But 
an  abundance  of  fat  fnakes  a  corresponding  elevation. 

Convulsions.  —  These  spasmodic  actions  are  due  to  dis- 
ordered action  of  the  muscles,  and,  further  back,  to  the 
disturbed  action  of  the  nervous  system  that  controls  the 
muscles.  Various  disturbances,  such  as  indigestion,  may 
by  reflex  action  bring  on  convulsions. 

Rigor  Mortis.  —  Rigor  mortis  (death  stiffening)  is  a 
muscular  rigidity  due  to  the  coagulation  of  muscle  plasma. 
It  usually  sets  in  not  long  after  death,  the  time  of  its 
appearance  and  its  duration  being  variable. 

Some  Prominent  Muscles.  — The  deltoid  on  the  shoul- 
der is  a  noticeable  muscle.  The  biceps  and  triceps  have 
already  been  studied.  The  calf  muscle  is  one  of  the 
thickest  and  strongest  in  the  body.  The  great  muscles  of 
the  rump  are  needed  to  raise  and  hold  the  body  up.  On 
each  side  of  the  front  of  the  neck  is  a  muscle  easily  ob- 
served in  thin  persons.  It  extends  down  to  the  top  of  the 
breast  bone. 

Sculpture  and  Anatomy.  — The  sculptor  needs  to  be  a 
thorough  student  of  anatomy,  so  far  as  the  bones  and  mus- 
cles are  concerned.  If  he  knows  the  muscles  thoroughly, 
he  can  make  them  "  stand  out "  naturally.  Otherwise  his 
work  cannot  be  truly  good. 


APPENDIX   A. 

ANTISEPTICS   AND   DISINFECTANTS. 

The  following  is  chiefly  from  Sternberg's  Manual  of  Bacteriology,  and 
embodies  part  of  the  report  of  "  The  Committee  on  Disinfectants  of  the 
American  Public  Health  Association." 

Antiseptic  Defined.  —  An  antiseptic  is  a  substance  having  the  power  to 
prevent  or  destroy  putrefaction,  or,  what  is  the  same -thing,  the  bacteria  upon 
which  putrefaction  depends. 

Disinfectant  Defined.  —  A  disinfectant  is  a  substance  that  can  destroy 
disease  germs. 

Disinfection  Defined.  —  Disinfection  is  the  destroying  of  disease  germs  by 
means  of  heat,  chemic  substances,  fumigation,  or  by  fresh  air. 

"The  injurious  consequences  which  are  likely  to  result  from  such  misap- 
prehension and  misuse  of  the  word  '  disinfectant '  will  be  appreciated  when  it 
is  known  that  recent  researches  have  demonstrated  that  many  of  the  agents 
which  have  been  found  useful  as  deodorizers  or  as  antiseptics  are  entirely 
without  value  for  the  destruction  of  disease  germs." 

An  Antiseptic,  but  not  a  Disinfectant.  —  "  This  is  true,  for  example,  as 
regards  the  sulphate  of  iron,  or  copperas,  a  salt  which  has  been  extensively 
used  with  the  idea  that  it  is  a  valuable  disinfectant.  As  a  matter  of  fact, 
sulphate  of  iron  in  saturated  solution  does  not  destroy  the  vitality  of  disease 
germs,  or  the  infecting  power  of  material  containing  them.  This  salt  is, 
nevertheless,  a  very  valuable  antiseptic,  and  its  low  price  makes  it  one  of  the 
most  valuable  agents  for  the  arrest  of  putrefactive  decomposition." 

EXTRACTS  FROM  THE  ABOVE-MENTIONED  REPORT. 

Some  Methods  of  Disinfecting. — "The  most  useful  agents  for  the 
destruction  of  spore-containing  infectious  material  are  :  — 

347 


348  PHYSIOLOGY. 

1.  Fire  ;    complete  destruction  by  burning. 

2.  Steam  under  pressure,  105  degrees  C.  (221  degrees  F.),  for  ten  minutes. 

3.  Boiling  in  water  for  half  an  hour. 

4.  Chloricl  of  lime  ;   a  four  per  cent  solution. 

5.  Mercuric  chlorid  ;   a  solution  of  I  :  500. 

For  the  destruction  of  material  which  owes  its  infecting  power  to  the  pres- 
ence of  microorganisms  not  containing  spores,  the  committee  recommends:  — 

1.  Fire;   complete  destruction  by  burning. 

2.  ISoiling  in  water  for  ten  minutes. 

3.  Dry  heat ;    no  degrees  C.  (230  degrees  F.)  for  two  hours. 

4.  Chlorid  of  lime  ;   a  two  per  cent  solution. 

5.  Solution  of  chlorinated  soda ;   a  ten  per  cent  solution. 

6.  Mercuric  chlorid  ;   a  solution  of  I  :  2,000. 

7.  Carbolic  acid  ;   a  five  per  cent  solution. 

8.  Sulphate  of  copper  ;   a  five  per  cent  solution. 

9.  Chlorid  of  zinc  ;  'a  ten  per  cent  solution. 

10.  Sulphur  dioxid  ;  exposure  for  at  least  twelve  hours  to  an  atmosphere 
containing  at  least  four  volumes  per  cent  of  this  gas  in  the  presence  of 
moisture. 

Methods  of  Disinfecting. — The  committee  would  make  the  following 
recommendations  with  reference  to  the  practical  application  of  these  agents 
for  disinfecting  purposes :  — 

For  Excreta.  —  (a)   In  the  sick  room  :  — 

1.  Chlorid  of  lime,  four  per  cent. 
In  the  absence  of  spores :  — 

2.  Carbolic  acid  in  solution,  five  per  cent. 

3.  Sulphate  of  copper  in  solution,  five  per  cent. 

(/>)   In  privy  vaults :  — 

1.  Mercuric  chlorid  in  solution,  I  :  500. 

2.  Carbolic  acid  in  solution,  five  per  cent. 

(c)  For  the  disinfection  and  deodori/alion  of  the  surface  of  masses  of 
organic  material  in  privy  vaults,  etc. :  — 

Chlorid  of  lime  in  powder. 

For  Clothing,  Bedding,  etc.  —  (a)  Soiled  underclothing,  bed  linen,  etc. 

1.  Destruction  by  fire,  if  of  little  value. 

2.  Boiling  at  least  half  an  hour. 


ANTISEPTICS  AND   DISINFECTANTS.  349 

3.  Immersion  in  a  solution  of  mercuric  chlorid  of  the  strength  of  I  :  2,000 
for  four  hours. 

4.  Immersion  in  a  two  per  cent  solution  of  carbolic  acid  for  four  hours. 

(b}  Outer  garments  of  wool  or  silk,  and  similar  articles,  which  would  be 
injured  by  immersion  in  boiling  water  or  in  a  disinfecting  solution  :  — 

1.  Exposure  in  a  suitable  apparatus  to  a  current  of  steam  for  ten  minutes. 

2.  Exposure  to   dry  heat  at  a  temperature  of   no  degrees  C.  (230  de- 
grees F.)  for  two  hours. 

(V)   Mattresses  and  blankets  soiled  by  the  discharge  of  the  sick  :  — 

1.  Destruction  by  fire.  * 

2.  Exposure  to  superheated  steam,  105  degrees  C.  (221  degrees  F.),  for 
ten  minutes.     (Mattresses  to  have  the  cover  removed  or  freely  exposed.) 

3.  Immersion  in  boiling  water  for  half  an  hour.     . 

Furniture  and  Articles  of  Wood,  Leather,  and  Porcelain.  — Washing, 
several  times  repeated,  with  :  — 

I.    Solution  of  carbolic  acid,  two  per  cent. 

For  the  Person.  — The  hands  and  general  surface  of  the  body  of  attend- 
ants of  the  sick,  and  of  convalescents,  should  be  washed  with  :  — 

1.  Solution  of  chlorinated  soda  diluted  with  nine  parts  of  water,  i  :  10. 

2.  Carbolic  acid  ;   two  per  cent  solution. 

3.  Mercuric  chlorid,  i :  l,ooo. 

For  the  Dead.  —  Envelop  the  body  in  a  sheet  thoroughly  saturated 
with :  — 

1.  Chlorid  of  lime  in  solution,  four  per  cent. 

2.  Mercuric  chlorid  in  solution,  i  :  500. 

3.  Carbolic  acid  in  solution,  five  per  cent. 

For  the  Sick  Room.  —  (a)  While  occupied,  wash  all  surfaces  with  :  — 

1.  Mercuric  chlorid  in  solution,  I  :  1,000. 

2.  Carbolic  acid  in  solution,  two  per  cent. 

(l>)  When  vacated,  fumigate  with  sulphur  dioxid  for  twelve  hours,  burning 
at  least  three  pounds  of  sulphur  for  every  thousand  cubic  feet  of- air  space  in 
the  room  ;  then  wash  all  surfaces  with  one  of  the  above-mentioned  solutions, 
and  afterward  with  soap  and  hot  water  ;  finally  throw  open  doors  and  win- 
dows, and  ventilate  freely." 


350 


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354  PHYSIOLOGY. 

Daily  Excretions.  — Sweat,  from  1.5  Ibs.  to  4.5  Ibs.  ;  urea,  about 
1  oz.  ;  organic  matter  exhaled,  :!  grains  ;  urine,  53  oz. 

"Of  the  entire  excreta,  32  per  cent  pass  off  by  the  breath  ;  17  per- 
cent by  the  skin  ;  4C.5  per  cent  by  the  kidneys  ;  4.5  per  cent  by  the 
alimentary  canal."  —  C'TTTKII. 

Number  of  Sweat  Glands.  —  The  number  of  sweat  glands  may 
be  as  high  as  3,500  in  a  square  inch,  and  the  average  is  estimated  at. 
2,800  per  square  inch  ;  as  there  are  about  2,500  square  inches  of  body 
surface,  it  is  readily  computed  that  there  are  several  millions  of  sweat, 
glands. 

Number  of  Hairs  on  the  Human  Head.  —  The  average  number 
of  hairs  on  the  head  is  120,000.  They  are  set  obliquely,  and  are  con- 
trolled by  muscles  so  that  they  may  be  made  to  stand  erect,  or  nearly  so, 
under  the  influence  of  certain  emotions,  as  fear,  anger,  etc. 

Huxley  and  others  have  classified  the  races  of  men  according  to  the 
hair,  into  the  Ulotrichi,  or  crisp  or  woolly  haired  division,  including 
the  negroes,  bushmen,  etc.  ;  and  Leiotrichi,  or  smooth-haired,  sub- 
divided into  the  Australioid,  the  Mongoloid,  the  Xanthochroic,  and  the 
Melanochroic. 

In  Europeans  the  hair  is  oval  in  cross-section  ;  in  the  Japanese 
and  Chinese  it  is  circular. 

Circulation.  —  Rate  of  blood  flow  :  in  the  large  arteries,  from  12  to 
16  inches  a  second  ;  in  the  caval  veins,  about  4  inches  a  second  ;  in  the 
capillaries,  from  1  inch  to  1.5  inches  a  minute.  A  portion  of  the  blood 
makes  the  complete  circulation  (in  a  horse)  in  less  than  half  a  minute. 
This  is  found  by  putting  some  readily  detected  chemical  into  one  jugular 
vein,  and  noting  how  soon  it  appears  in  the  other  jugular  vein.  The 
time  necessary  for  all  the  blood  to  pass  through  the  heart  is  estimated 
as  follows  :  Each  ventricle  pumps  about  six  ounces  of  blood  at  each 
stroke.  At  this  rate  thirty  strokes,  25  to  50  seconds  (or  less),  would 
have  pumped  all  the  blood  in  the  body.  Still,  some  of  the  blood  (from 
the  shorter  circuits)  may  have  been  pumped  twice,  and  some  (from  the 
longer  routes)  may  not  yet  have  been  around  once.  And  since  the 
total  amount  of  blood  has  been  only  approximately  determined,  these 
figures  are  not  very  accurate. 

Number  of  blood  corpuscles  to  the  cubic  inch,  about  83,000,000. 

Dr.  Tanner's  Forty  Days'  Fast  (Newspaper  Account).  No 
Food  but  "Water  Taken.  —  When  Dr.  Tanner  came  to  New  York 
from  Minnesota  he  weighed  184  pounds.  He  was  six  weeks  making  ar- 


VITAL  STATISTICS. 


355 


rangernents  for  his  fast;  and  when  lie  began  his  experiment  his  weight 
was  157£  pounds.  He  weighed  121  £  pounds  on  the  day  his  fast  ended. 
He  had  therefore  lost  62 \  pounds  since  he  came  to  the  city,  and  3(3 
pounds  since  he  began  his  fast.  Dr.  Hammond,  the  well-known  New 
York  physician  whose  assertion  that  a  forty  days'  fast  was  a  physical 
impossibility  led  Dr.  Tanner  to  make  the  attempt,  came  out  in  "a  card 
in  the  New  York  papers  declaring  that  he  believed  the  fast  had  been 
fairly  conducted. 

On  each  day  of  his  fast  Dr.  Tanner  weighed  as  follows  :  — 


DAY. 

1st  

POUNDS. 

DAY. 

25th 

POUNDS. 

1314, 

3d  

...  153 

20th  

.  "  .  .  .  .  I3ld 

5th  
7th  

.  .  .  147£ 
.  1434 

27th  ..... 
28th  .  . 

129! 

llth  
13th  
14th 

.  .  .  139| 
133 

29th  ..... 
30th  
31st 

130 

16th  

.  .  .  132 

32d 

1274 

17th  (8.30  P.M.)  .  . 
17th  (HAM) 

135^ 

33d  
34th  

i2e| 

18th  
19th 

136 

35th  
36th  .  ... 

20th  (4  P.M.)  .  .  . 
20th  (5  A.M.)  .  .  . 
21st  . 

.  .  .  .  135 

.  .  .  .  1  35 

37th  
38th  
39th  

1224 

22d 

1334 

40th 

1214 

26th  ...... 

Cavities  of  the  Body.  —  1.  Mucous  cavities  (open  to  the  external 
air).  Digestive  tube,  respiratory  passages,  genito-urinary  passages,  ex- 
ternal and  middle  ear,  etc. 

2.  Serous  cavities  (closed).     They  may  all  be  said  to  be  lymph  cav- 
ities.    They  are  the  lymph  spaces  throughout  the  body,  and  the  large 
spaces,  called  the  pleural  cavity  around  the  lungs,  the  pericardial  cavity 
around  the  heart,  the  peritoneal  cavity  in  the  abdomen,  the  arachnoid 
cavity  around  the  brain,  and  a  similar  one  along  the  spinal  cord. 

3.  Synovial  cavities  in  the  joints. 

4.  Blood  cavities,  —  the  inside  of  the  heart  and  blood  tubes. 

5.  Secretion  cavities,  —  the  cavities  and  tubes  from  the  glands  ;  for 
example,  the  bile  sac  and  its  duct. 

6.  Bone  cavities. 


356 


PHYSIOLOGY. 


LOSSES  OF  THE  TISSUES  DURING  STARVATION*. 
(FROM  KXPKRIMEXT  ON  A  CAT.) 


Fat los«'s«»:'.  per  i-»Mit. 

Blood     ....  ••;.-> 

Spleen     ....  "71  " 

Pancreas     ...  "64  " 

Stomach      ...  "39  " 

Pharynx,  gullet  .  "     34  " 

Skin "     33  " 

Kidneys.    ...  "31  " 

Liver .  "     52  " 


Heart      .... 

Intestines    .    .     . 

Muscles  of  locomo- 
tion .... 

Respiratory  appa- 
ratus .  .  . 

Bones      .... 

Eyes 

Nervous  system  . 


loses  44  per  cent. 

"  42 

"  42  " 

"  22  " 

"  16 

"  10  " 

"  2  " 


QUANTITY  OF  WATER  IN   1,000  PARTS. 

Teeth 100  Bile 880 

Bones 130  Milk H87 

Cartilage 550  Pancreatic  juice 900 

Muscles 750  Urine 936 

Ligament 768  Lymph 960 

Brain *   .    .  789  Gastric  juice 975 

Blood 795  Sweat 986 

Synovia 805  Saliva W"> 

THE  LOSS  OF  WATER  FROM  THE  BODY. 

From  the  Alimentary  canal  (feces) 4  per  cent. 

"    Lungs 20 

"        "    Skin  (perspiration) 30         " 

"        "    Kidneys  (urine) 46         " 

ELEMENTS  IN  THE    HUMAN  BODY. 

Oxygen 72.0  Chlorin .085 

Carbon 13.5  Fluorin 08 

Hydrogen 9.1  Potassium .026 

Nitrogen 2.5  Iron 01 

Calcium 1.3  Magnesium 0012 

Fosforus 1.15  Silicon 0002 

Sulfur 147  Copper,  lead,  aluminum   .     (traces) 

Sodium 1  100. 

DAILY  RATION  OF  A  U.   S.   SOLDIER  DURING  THE  LATE  WAR. 

Bread  or  flour 22        oz. 

Fresh  or  salt  beef  (or  pork  or  bacon  12  oz.) 20 

Potatoes  (three  times  a  week) 16         " 


VITAL  STATISTICS. 


357 


Rice  
Coffee  (or  tea  0-.24  oz.)     .     . 

.     ...    1.6 
...    1.6 
.     .     .     .   2.4 

64 

Vinegar      •     • 
Salt   •     

COMPOSITION  OF  F< 

WATKU.        PROTEIDS. 

32 

30DS. 

FATS. 

16 

CARBO- 

HYDRATES. 

Beef,  lean   

72 

19.3 

3.6 

Beef,  fat      

51 

14.8 

29.8 

Mutton,  lean  .... 

72 

18.3 

4.9 

Mutton,  fat     .... 

53 

12.4 

31.1 

Veal  

63 

16.5 

15.3 

Pork,  fat     

39 

9.8 

48.9 

Poultry  

74 

21 

3.8 

Whitefish   

78 

18.1 

2.9 

Salmon  

77 

16.1 

5.5 

Eels  (rich  in  fat)     .     . 

75 

9.9 

13.8 

Oysters  

75.7 

11.7 

2.4 

SUGAR. 

Milk  

86 

4.1 

3.9 

5.2 

Buttermilk      .... 

88 

4.1 

.7 

6.4 

Cream    

66 

2.7 

26.7 

2.8 

Cheese,  full     .... 

36 

28.4 

31.1 

.  .  . 

Cheese,  skim  .... 

44 

44.8 

6.3 

Eggs,  white     .     .     .     . 

78 

20.4 

Eggs,  yelk  .     .    ... 

52 

16 

30.7 

.  .  . 

STARCH. 

Bread      

37 

8.1 

1.6 

51 

Flour  

15 

10.8 

2 

70.8 

COMPOSITION 

OF  THE 

BLOOD. 

Water  

Solids  — 

Corpuscles    .... 

.     130 

Proteids  (of  serum) 

.      70 

Fibrin  (of  clot)      .     . 

2.2 

Fatty  matters  (of  serum)  

1.4 

Inorganic  salts      .     . 

6.0 

Gases,  urea,  kreatin, 

etc.  .     . 

6.4 

gill. 


5.1 
4.4 

4.8 

4.7 
2.3 
1.2 
1.0 
1.4 
2.7 
2.7 

.8 
.8 
4.9 
4.5 
4.9 
1.6 
1.3 

2.3 
1.7 


784 


216 
1000 


358  PHYSIOLOGY. 

COMPOSITION  OF   CASTKK'   ,11  K'K. 

Water 99.44 

Solids  — 

Pepsin 319 

Salts 218 

Hydrochloric  acid 02 

.557 
100 

Fluids  of  the  Body  (FORD).  —  1.  Circulating  fluids,  —  chyle, 
lymph,  blood. 

2.  Fluids  for  digestion,  —  saliva,  gastric  juice,  pancreatic  juice,  bile, 
intestinal  juice. 

3.  Fluids  of  closed  cavities,  —  of  the  arachnoid,  pleura!,  pericardia!, 
and  peritoneal  sacs,  of  joints,  of  the  eye  and  ear,  and  of  cells. 

4.  Secretions  for  protection,  — cerumen  or  wax,  tears,  fluid  of  mucous 
membranes,  oily  fluids  on  the  surface  of  the  body. 

5.  Fluids  for  discharge,  —  intestinal  secretion,  renal  or  kidney  se- 
cretion, perspiration,  vapor  from  the  lungs,  etc. 

Acids  and  Alkalies  of  the  Body.  —  Acids, — gastric  juice,  mu- 
cus, chyme,  contents  of  large  intestine. 

Alkalies,  —  saliva  (or  neutral),  pancreatic  juice,  intestinal  juice, 
bile  (or  neutral),  contents  of  small  intestine,  sweat. 

Amount  of  Digestive  Liquids.  —  The  amount  of  saliva  secreted 
daily  is  estimated  at  from  1  to  3  pints,  of  gastric  juice  from  10  to  20  pints, 
of  bile  from  2  to  3  pints.  The  amount  of  intestinal  and  other  juices  is 
difficult  to  estimate.  But  it  is  readily  seen  that  a  very  large  amount  of 
liquid  is  daily  separated  from  the  blood  to  be  used  in  the  preparation  of 
the  food  for  absorption  into  the  blood.  This  is  to  be  looked  upon  as  an 
investment.  It  is  supposed  to  be  reabsorbed  with  large  returns  in  addi- 
tion to  the  prepared  food ;  and  if  anything  interferes  with  the  absorp- 
tion of  the  food  material,  especially  if  the  secretion  goes  on,  it  is  plain 
that  bankruptcy  will  follow  as  surely  as  in  the  business  world  whenever 
there  is  a  continual  expenditure  without  corresponding  returns.  The 
condition  known  as  "diarrhea"  illustrates  this  condition,  perhaps,  as 
well  as  any  well-known  condition  of  the  body. 

Specific  Gravity  of  the  Liquids  of  the  Body.  —  As  all  the 
liquids  of  the  body  have  dissolved  and  suspended  in  them  various  salts 
and  other  matters,  they  are  all  heavier  than  water. 


VITAL   STATISTICS.  359 

Alcohol  and  Longevity.  —  Investigation  by  Baer  has  shown  that  the 
average  expectation  of  life  among  users  and  dealers  in  alcoholic  liquors 
is  very  much  shortened.  The  following  table  gives  a  comparative  view  of 
the  expectation  of  life  in  those  who  abstained  from  and  those  who  used 
alcohol :  — 

EXPECTATION   OF    LIFE. 

AGE.  ABSTAINERS.  ALCOHOL    USERS 

At  25,  32.08  years,  26.23  years. 

"'  35,  25.92      "  20.01       " 

"   45  J9.92     "  *          i$.i9     " 

"   55'  '4-45     "  "-16    " 

"  65,  9.62     "  8.04    " 


TABLE  SHOWING  THE  INFLUENCE  OF  ALCOHOL   UPON   THE 
MORTALITY  FROM  VARIOUS  DISEASES. 

GENERAL    MALE    POPULATION.  ALCOHOL   VENDERS. 

Brain  disease,  11.77  Per  cent-  r4-43  per  cent. 

Tuberculosis,  30.36  "  36.57  " 

Pneumonia  and  pleuritis,  9.63  "  H-44  " 

Heart  disease,  1.46  "  3.29  " 

Kidney  disease,  1.40  "  2.11  " 

Suicide,  2.99  "  4.02  " 

Cancer,  2.49  "  3.70  " 

Old  age,  22.49  "  7-°5  " 


GLOS  BA  RY. 


Albumen  (al-bu'-meri).     The  white  of  an  egg. 

Albumin  (iil-hi'i'-min).  A  proteid  substance,  the  chief  constituent  of 
the  body.  Its  molecule  is  highly  complex,  and  varies  widely  within 
certain  limits  in  different  organs  and  in  different  conditions. 

Albuminuria  (al-bu'-mi-nu'-ri-a}.  The  presence  of  albumin  in  tin-  urine, 
indicating  changes  in  the  blood  or  in  the  kidneys. 

Amylopsin  (am-i-lop'-xin}.     A  ferment  said  to  exist  in  pancreatin. 

Anabolism  (an-ab'-o-lizm}.  Synthetic  or  constructive  metabolism. 
Activity  and  repair  of  function  ;  opposed  to  katabolism. 

Arbor  Vitae  (ar'-6or  vl'-te).  A  term  applied  to  the  branched  appear- 
ance of  a  section  of  the  cerebellum. 

Argon  (ar'-gron).  A  newly  discovered  element  similar  to  nitrogen 
(found  in  the  air). 

Arytenoid  (ar-i-te'-noid}.  Resembling  the  mouth  of  a  pitcher,  as  the 
arytenoid  cartilages  of  the  larynx. 

Atlas  (at'-las).  The  uppermost  of  the  cervical  vertebrae  (from  the 
mythical  Atlas  who  supported  the  Earth). 

Auricle  (aw'-ri-kl).  The  auricles  of  the  heart  are  the  two  cavities  be- 
tween the  veins  and  the  ventricles.  Also,  the  pinna  and  external 
meatus  of  the  ear. 

Axis  (ak'-sis).  The  second  cervical  vertebra,  on  which  the  head,  with 
the  atlas,  turns. 

Bacterium  (bak-te'-ri-um},  pi.  bacteria.  A  genus  of  microscopic  fungi 
characterized  by  short,  linear,  inflexible,  rod-like  forms  —  without 
tendency  to  unite  into  chains  or  filaments. 

Biceps  (bl'-seps}.     Biceps  brachii,  the  flexor  of  the  arm. 

Bicuspid  (bi-kus'-pid}.  Having  two  points  ;  the  bicuspid  or  premolar 
teeth;  the  bicuspid  valve,  between  the  left  auricle  and  the  left  ven- 
tricle. 

Brachial  (bra'-ke-al  or  brak'-i-al}.     Pertaining  to  the  arm. 

360 


GLOSSARY.  361 

Bronchus  (brong' -kits'),  pi.  bronchi.  The  two  tubes  into  which  the  tra- 
chea divides  opposite  the  third  thoracic  vertebra,  called  respectively 
the  right  and  left  bronchus. 

Caffein  (kaf'-e-in').  An  alkaloid  that  occurs  in  the  leaves  and  beans  of 
the  coffee-tree,  in  Paraguay  tea,  etc. 

Canaliculus  (kan-a-Uk'-u-lus^),  pi.  canaliculi.  The  crevices  extending 
from  lacunae,  through  which  nutrition  is  conveyed  to  all  parts  of 
the  bone. 

Canine  (ka-nl)i'  or  ka'-nin*).  The  conical  teeth  between  the  incisors 
and  the  premolars. 

Capillary  (kap'-i-la-ri  or  ka-pil'-a-ri).  A  minute  blood-tube  connecting 
the  smallest  ramification  of  the  arteries  with  those  of  the  veins. 

Capsule  (kap'-auV).  A  tunic  or  bag  that  incloses  a  part  of  the  body  or 
an  organ. 

Carbohydrate  (kar-bo-hi'-draf).  An  organic  substance  containing  six 
carbon  atoms  or  some  multiple  of  six,  and  hydrogen  and  oxygen  in 
the  proportion  in  which  they  form  water;  that  is,  twice  as  many 
hydrogen  as  oxygen  atoms.  Starches,  sugars,  and  gums  are  carbo- 
hydrates. 

Cardiac  (kar'-di-ak}.     Pertaining  to  the  heart. 

Carotid  (ka-rot'-id}.     The  principal  right  and  left  arteries  of  the  neck. 

Carpus  (kar'-pus).     Belonging  to  the  wrist;  as  the  carpal  bones. 

Cartilage  (kar'-ti-luj}.     Gristle  of  various  kinds,  articular,  etc. 

Casein  (ka'-se-m).  A  derived  albumin,  the  chief  proteid  of  milk,  pre- 
cipitated by  acids  and  by  rennet  at  40°C. 

Cecum  (se'-kum).  The  large  blind  pouch  or  cul-de-sac,  in  which  the 
large  intestine  begins. 

Centrum  (sen'-trum).  The  center  or  middle  part  ;  the  body  of  a  verte- 
bra, exclusive  of  the  bases  of  the  neural  arches. 

Cerebellum  (ser-e-bel'-um*).  The  inferior  part  of  the  brain,  lying  below 
the  cerebrum. 

Cerebrum  (ser'-e-brum').  The  chief  portion  of  the  brain,  occupying  the 
whole  upper  part  of  the  cranium. 

Cervical  (ser'-m-kal}.     Pertaining  to  the  neck,  as  cervical  vertebrae. 

Chordae  tendineae  (kor'-de}.  The  tendinous  cords  connecting  the 
fleshy  columns  of  the  heart  with  the  auriculo-ventricular  valves. 

Choroid  (ko'-roid}.  The  second  or  vascular  coat  of  the  eye,  continu- 
ous with  the  iris  in  front,  and  lying  between  the  sclerotic  and  the 
retina. 


362 

Chyle  (kll).  The  milk-white  fluid  absorbed  by  tin-  lacteals  during  di- 
gestion. 

Chyme  (kirn').  Food  that  has  undergone  gastric  digestion,  and  has  not 
yet  been  acted  upon  hy  the  biliary,  pancreatic,  and  intestinal 
secretions. 

Cilium  (stT-i-um),  pi.  cilia.  The  eyelashes;  also  the  hair-like  appen- 
dages of  certain  epithelial  cells,  whose  function  is  to  propel  fluid 
or  particles  along  the  passages  that  they  line. 

Ciliary  (sil'-i-a-ri).  Pertaining  to  the  eyelid  or  eyelash  ;  also  by  ex- 
tension to  the  ciliary  apparatus  or  the  structure  related  to  the 
mechanism  of  accommodation.  Pertaining  to  the  cilia. 

Circumvallate  (sir-kum-val'-at).  Surrounded  by  a  wall  or  prominence, 
as  the  circumvallate  papillae  on  the  tongue. 

Clavicle  (klav'-i-kl).     The  collar-bone. 

Coccyx  (kok'-siks).  The  last  bone  of  the  spinal  column,  formed  by  the 
union  of  four  rudimentary  vertebrae. 

Cochlea  (kok'-le-a).  A  cavity  of  the  internal  ear,  resembling  a  snail- 
shell. 

Conjunctiva  (kon-junyk-ti'-va).  The  mucous  membrane  covering  the 
anterior  portion  of  the  globe  of  the  eye,  reflected  on,  and  extending 
to,  the  free  edge  of  the  lids. 

Corpus  Arantii  (kor'-pus).  The  tubercles,  one  in  the  center  of  each 
segment  of  the  semilunar  valves. 

Corpuscle  (kor'-pus-l).  A  name  loosely  applied  to  almost  any  small, 
rounded  or  oval  body,  as  the  blood  corpuscles. 

Cortex  (kor'-teks}.  Bark.  The  outer  layer  of  gray  matter  of  the  brain  ; 
the  outer  layer,  cortical  substance,  of  the  kidney. 

Cricoid  (krl'-koid}.  Ring-shaped,  as  the  cricoid  cartilage  of  the 
larynx. 

Dentine  (den'-tin}.  The  ivory-like  substance  constituting  the  bulk  of 
the  tooth,  lying  under  the  enamel  of  the  crown  and  the  cement 
of  the  root. 

Diabetes  (di-a-be'-tez*}.  The  name  of  two  different  affections,  diuln-t<-x 
mellitn*,  or  persistent  glycosuria,  and  diabetes  insipidus,  or  polyu- 
ria,  both  characterized,  in  ordinary  cases,  by  an  abnormally  large 
discharge  of  urine.  The  former  is  distinguished  by  the  presence 
of  an  excessive  quantity  of  sugar  in  the  urine. 

Dialysis  (di-ar-i-*is\  The  operation  of  separating  crystalline  from 
colloid  substances  by  means  of  a  porous  diaphragm,  the  former 


GLOSSARY.  363 

passing  through  the  diaphragm  into  the  pure  water  upon  which  the 
dialyzer  rests. 

Digastric  (di-yas'-trik).  Having  two  bellies,  as  the  digastric  muscle, 
enlarged  near  each  end  and  with  a  tendon  in  the  middle. 

Duodenum  (du-d-de'-num).  The  first  part  of  the  small  intestine,  begin- 
ning with  the  pylorus. 

Emulsion  (e-inul'-shun}.  Water  or  other  liquid  in  which  oil,  in  minute 
subdivision  of  its  particles,  is  suspended. 

Enamel  (eM-am'~el).     The  hard  covering  of  the  crown  of  a  tooth. 

Endothelium  (en-do-the'-li-um).  The  internal  lining  membrane  of 
serous,  synovial,  and  other  internal  surfaces,  the  homolog  of  epi- 
thelium. 

Enzyme  (en'-zim}.  Any  chemic  or  hydrolytic  ferment,  as  distinguished 
from  organized  ferments  such  as  yeast;  unorganized  ferment. 

Epiglottis  (ep-i-ylot'-is).  A  thin  fibro-cartilaginous  valve  that  aids  in 
preventing  food  and  drink  from  passing  into  the  larynx. 

Esophagus  (e-8Q/y-a-grt*«).  The  musculo-membranous  tube  extending 
from  the  pharynx  to  the  stomach. 

Eustachian  (u-sta'-ki-an).  Eustachian  tube,  the  tube  leading  from  the 
middle  ear  to  the  pharynx. 

Facet  (fas'-et}.  A  small  plane  surface.  The  articulating  surface  of  a 
bone. 

Femur  (/e'-mer).     The  thigh-bone. 

Ferment  (fer'-ment}.  Any  micro-organism,  proteid,  or  other  chemic 
substance  capable  of  producing  fermentation,  i.e.,  the  oxidation 
and  disorganization  of  the  carbohydrates. 

Fibrin  (fi'-brin}.  A  native  albumen  or  proteid,  a  substance  that,  be- 
coming solid  in  shed  blood,  plasma,  and  lymph,  causes  coagulation 
of  these  fluids. 

Fibula  (fib'-u-la}.  The  smaller  or  splint  bone  in  the  outer  part  of  the 
leg,  articulating  above  with  the  tibia,  and  below  with  the  astraga- 
lus and  tibia. 

Filiform  (Jll'-i-forni).     Thread-like,  as  the  filiform  papillae. 

Frontal  (fron'-tal).     Belonging  to  the  front,  as  the  frontal  bone. 

Fungiform  (fun'-ji-form).  Having  the  form  of  a  mushroom,  as  fungi- 
form  papillae. 

Ganglion  (yany'-gli-on\  pi.  ganglions  or  ganglia.  A  separate  and  semi- 
independent  nervous  center,  communicating  with  other  ganglia  or 
nerves,  with  the  central  nervous  system,  and  peripheral  organs. 


364 

Gastric  (yas'-trik^).     Pertaining  to  the  stomach. 

Gelatin  (jel'-a-tin).  An  albuminoid  substance  of  jelly-like  consistence, 
obtained  by  boiling  skin,  connective  tissue,  and  bones  of  animals 
in  water.  The  glue  of  commerce  is  an  impure  variety. 

Glosso-pharyngeal  (glox'-o-fa-rin'-je-al).  Pertaining  to  the  tongue  and 
larynx. 

Gluten  (ylo'-ten).  A  substance  resembling  albumin,  and  with  which  it 
is  probably  identified  ;  it  occurs  abundantly  in  the  seeds  of  cereals. 

Glycogen  (yll'-ko-jen}.  A  white  amorphous  powder,  tasteless  and  odor- 
less, forming  an  opalescent  solution  with  water,  and  insoluble  in 
alcohol.  It  is  commonly  known  as  animal  starch.  It  occurs  in  the 
blood  and  in  the  liver,  by  which  it  is  elaborated,  and  is  changed  by 
diastasic  ferments  into  glucose. 

Gustatory  (gus'-ta-to-ri}.  Pertaining  to  the  special  sense  of  taste  and 
its  organs. 

Hashish  (JtaM'-etA).  A  preparation  from  Indian  hemp,  Cannabis  in- 
dica.  It  is  a  powerful  narcotic. 

Haversian  (ha-ver'-zian*).  Haversian  canal,  in  bone,  a  central  opening 
for  blood-tubes,  surrounded  by  a  number  of  concentric  rings,  or 
lamellae,  of  bone. 

Hemoglobin  (hem-o-ylo'-bin}.  A  substance  existing  in  the  corpuscles  of 
the  blood,  and  to  which  their  red  color  is  due. 

Hepatic  (he-pat' -ik).     Pertaining  or  belonging  to  the  liver. 

Hilum  (hl'-lum}.  A  small  pit,  scar,  or  opening  in  an  organic  structure  ; 
the  notch  on  the  internal  or  concave  border  of  the  kidney. 

Humerus  (hu'-me-rus}.     The  bone  of  the  upper  arm. 

Humor  (/m'-wor).     Any  liquid,  or  semi-liquid,  part  of  the  body. 

Hyoid  (hl'-oid}.  Having  the  form  of  the  letter  U.  The  hyoid  bone 
situated  between  the  root  of  the  tongue  and  the  larynx,  supporting 
the  tongue  and  giving  attachment  to  its  muscles. 

Hypo-glossal  (hi-po-ylos'-al}.     Under  the  tongue. 

Iliac  (tT-t-rtJfc).  Pertaining  to  the  ilium,  or  region  of  the  flanks,  as  iliac 
artery,  vein,  etc. 

Incisor  (m-sf-sor).     The  chisel-shaped  front  teeth. 

Inhibition  (in-hi-bish'-un).  The  act  of  checking,  restraining,  or  sup- 
pressing ;  any  influence  that  controls,  retards,  or  restrains.  Inhib- 
itory nerves  and  centers  are  those  intermediating  a  modification, 
stoppage,  or  suppression  of  a  motor  or  secretory  act  already  in 
progress. 


GLOSSARY.  365 

Innominate  (i-nom'-i-nate).  Nameless  ;  a  term  applied  to  several  parts 
of  the  body  to  which  no  other  definite  name  has  been  given,  as  the 
innominate  bone,  artery,  vein,  etc. 

Invertin  (in'-ver-tln\  A  ferment  found  in  the  intestinal  juice,  and  also 
produced  by  several  species  of  plants  ;  it  converts  cane-sugar  in 
solution  into  invert  sugar. 

Jugular  (jo'-gu-lar^.     Pertaining  to  the  throat,  as  the  jugular  vein. 

Katabolism  (ka-tab'-o-lizm).  Analytic  or  destructive  metabolism  ;  a 
physiologic  disintegration  ;  opposed  to  anabolism. 

Lacrymal  (lak'-ri-mal}.  Having  relation  to  the  organs  of  the  secretion, 
transfer,  or  excretion  of  tears. 

Lacuna  (la-ku'-na}.  A  little  hollow  space  ;  especially  the  microscopic 
cavities  in  bone  occupied  by  the  bone  corpuscles,  and  communicat- 
ing with  one  another  and  with  the  haversian  canals  and  the  sur- 
faces of  the  bone  through  the  canaliculi. 

Lamella  (fti-mel'-a),  pi.  lamellae.  A  thin  lamina,  scale,  or  plate  ;  of 
bone,  the  concentric  rings  surrounding  the  haversian  canals. 

Larynx  (lar'-inyks).  The  upper  part  of  the  air  passage  between  the 
trachea  and  the  base  of  the  tongue  ;  the  voice-box. 

Legumin  (le-grw'-rain).  A  proteid  compound  in  the  seeds  of  many  plants 
belonging  to  the  natural  order  Leguminosae  (peas,  beans,  lentils, 
etc.). 

Lumbar  (lum'-bcir\  pertaining  to  the  loins,  especially  to  the  region 
about  the  loins. 

Lymphatic  (lim-fat'-ik}.     Pertaining  to  lymph. 

Lymphatics  (lim-fat'-iks).     The  tubes  that  convey  lymph. 

Lymphatic  glands.  The  glands  intercalated  in  the  pathway  of  the 
lymphatic  tubes,  through  which  lymph  is  filtered. 

Massage  (ma-sazh').  A  method  of  effecting  changes  in  the  local  and 
general  nutrition,  action  and  other  functions  of  the  body,  by  rub- 
bing, kneading,  and  other  manipulation  of  the  superficial  parts  of 
the  body  by  the  hand  or  an  instrument. 

Masseter  (mas'-e-ter^).  A  chewing-muscle  felt  on  the  angle  of  the 
jaw. 

Medullary  (med'-u-la-ri}.  Pertaining  to  the  medulla,  or  marrow  ;  re- 
sembling marrow.  Also  pertaining  to  the  white  substance  of  the 
brain  contained  within  the  cortical  envelop  of  gray  matter. 

Mesenteric  (mez-en-ter'-ik}.  Pertaining  to  the  mesentery,  as  artery, 
vein,  etc. 


366  GLOSS.  IK}: 

Mesentery  ^nez'-cn-lrr-i}.  A  fold  of  the  peritoneum  that  connects  cer- 
tain portions  of  the  intestine  with  the  dorsal  abdominal  wall. 

Metabolism  (me-ta&'-d-Jtem).  A  change  in  the  intimate  condition  of 
cells  ;  (1)  constructive  or  synthetic  metabolism  is  called  Anabo- 
lism  ;  in  anabolism,  the  substance  is  becoming  more  complex  and 
is  accumulating  force  ;  (2)  destructive  or  analytic  metabolism  is 
called  Katabolism  :  in  katabolism  there  is  disintegration,  the  mate- 
rial is  becoming  less  complex,  and  there  is  loss  or  expenditure  of 
force. 

Metacarpus  (met-a-kirr'-imx).     The  bones  of  the  palm  of  the  hand. 

Metatarsus  (met-a-tar'-ms).  The  five  bones  of  the  arch  of  the  foot, 
situated  between  the  tarsus  and  the  phalanges. 

Mitral  (nil'-trtil).  Resembling  a  miter;  mitral  valve,  with  two  Hups, 
between  the  left  auricle  and  the  left  ventricle. 

Molar  (mo'-far).     Mill;  the  grinding-teeth. 

Mucous  (wu'-fctw).     A  term  applied  to  those  tissues  that  secrete  mucus. 

Mucus  (mu'-kus).  A  viscid  liquid  secretion  of  mucous  membranes, 
composed  essentially  of  inucin,  holding  in  suspension  desquamated 
epithelial  cells,  etc. 

Myosin  (  wi'-o-sm).  A  proteid  of  the  globulin  class,  —  the  chief  proteid 
of  muscle.  Its  coagulation  after  death  causes  riyor  mortis. 

Narcosis  (nar-ko'-sis) .  The  deadening  of  pain,  or  production  of  incom- 
plete or  complete  anesthesia  by  the  use  of  narcotic  agents,  such  as 
anesthetics,  opium,  and  other  drugs. 

Narcotic  (nar-kotf-ic}.     A  drug  that  produces  narcosis. 

Neural  (nu'-ral).     Pertaining  to  the  nerves. 

Neuroglia  (nu-rog'-li-a*).  The  reticulated  framework  or  skeleton-work 
of  the  substance  of  the  brain  and  spinal  cord.  The  term  is  some- 
times abbreviated  to  glia. 

Nucleus  (nu'-kle-us).  The  essential  part  of  a  typical  cell,  usually  round 
in  outline,  and  situated  in  the  center. 

Occipital  (ok-sip'-i-tal}.  Pertaining  to  the  occiput  or  back  part  of  the 
head,  as  the  occipital  bone. 

Odontoid  (o-don'-toid).  Resembling  a  tooth  ;  the  tooth-like  process 
(axis)  of  the  second  cervical  vertebra,  on  which  the  atlas  turns. 

Olfactory  (ol-fak'-to-ri}.     Pertaining  to  the  sense  of  smell. 

Osmosis  (os-wio'-sts)-  That  property  by  which  liquids  and  crystalline 
substances  in  solution  pass  through  porous  septa ;  endosmosis  and 
exosmosis. 


GLOSSARY.  367 

Oxy-hemoglobin  (ok-ai-hem-o-ylo'-bin).  Hemoglobin  united,  molecule 
for  molecule,  with  oxygen.  It  is  the  characteristic  constituent  of 
the  red  corpuscles  to  which  the  scarlet  color  of  arterial  blood  is 
due. 

Pancreas  (pan'-krc-as^.  A  large  racemose  gland  lying  transversely 
across  the  dorsal  wall  of  the  abdomen.  It  secretes  a  clear  liquid 
for  the  digestion  of  proteids,  fats,  and  carbohydrates.  The  sweet- 
bread of  animals,  vulgarly  called  the  "belly  sweet-bread"  in  con- 
tra-distinction  to  the  thymus,  or  true  sweet-bread. 

Pancreatin  (pan'-krv-a-t'm}.    The  active  element  of  the  pancreatic  juice. 

Papilla  (pa-pil'-a},  pi.  papillae.  Any  soft,  conical  elevation,  as  papillae 
of  the  dermis,  tongue,  etc. 

Papillary  (pap'-i-la-ri}.  Pertaining  to  a  papilla;  papillary  muscles, — 
the  conic  muscular  columns  of  the  heart,  to  which  the  chordae 
tendineae  are  attached. 

Parietal  (pa-ri'-e-tal).     Pertaining  to  the  walls,  as  the  parietal  bone. 

Parotid  (pa-rot'-id).     Near  the  ear,  as  the  parotid  salivary  glands. 

Patella  (pa-tel'-a}.     The  knee-pan. 

Peptone  (pep'-ton}.  A  proteid  body  produced  by  the  action  of  peptic 
and  pancreatic  digestion. 

Pericardium  (per-i-kar'-di-um}.  The  closed  membranous  sac  or  cover- 
ing, that  envelops  the  heart. 

Periosteum  (per-i-os'-te-um*).  A  fibrous  membrane  that  invests  the 
surfaces  of  the  bones,  except  at  the  points  of  tendinous  and  liga- 
mentary  attachments,  and  on  the  articular  surfaces  where  cartilage 
is  substituted. 

Peristaltic  (per-i-stal'-tik}.  The  peculiar  movement  of  the  intestine 
and  other  tubular  organs,  consisting  in  a  vermicular  shortening 
and  narrowing  of  the  tube,  thus  propelling  the  contents  onward. 
It  is  due  to  the  successive  contractions  of  the  bundles  of  longitudi- 
nal and  circular  muscular  fibers. 

Peritoneal  (per-i-to-ne'-al}.     Pertaining  to  the  peritoneum. 

Peritoneum  (per-l-to-ne'-um*).  The  serous  membrane  lining  the  interior 
of  the  abdominal  cavity,  and  surrounding  the  contained  viscera. 
The  peritoneum  forms  a  closed  sac,  but  is  rendered  complex  in  its 
arrangement  by  numerous  foldings  produced  by  its  reflection  upon 
the  viscera. 

Phalanges  (fa-lan'-jez),  plural  of  phalanx  (fa'-lanyks~).  Any  one  of 
the  bones  of  the  fingers  or  toes. 


368  GLOSS.  1A'\  \ 


Pharynx  ^/•'-/m/^-     The  cavity  back  of  the  soft  palate.     It  commu- 

nicates anteriorly  with  the  posterior  nares,  laterally  with  the  eusta- 

chian  tubes,   ventrally  with  the   mouth,  and  posteriorly  with  the 

gullet  and  larynx. 
Plasma  (plaz'-ma).    The  original  undifferentiated  substance  of  IUIM  rut, 

living  matter.     The  fluid  part  of  the  blood  and  lymph. 
Pleura  (]>Hj'-rii).     The  serous  membrane  which  envelops  the  lungs,  and 

which,  being  reflected  back,  lines  the  inner  surface  of  the  thorax. 
Plexus  (plek'-sus).     An  aggregation  of  vessels  or  nerves  forming  an 

intricate  net-work. 
Pneumogastric  (nu-md-gas'-trik).     Pertaining  conjointly  to   the  lungs 

and  the  stomach,  or  to  the  pneumogastric  or  vagus  nerve. 
Portal  (por'-tal).     Pertaining  to  the  porta  (gate)  or  hi  him  of  an  organ, 

especially  of  the  liver,  as  the  portal  vein. 
Postcaval  (post-ka'-ioal}.     Pertaining   to  the  postcava;   the  postcaval 

vein,  formerly  called  the  inferior  vena  cava,  or  vena  cava  ascendens. 
Precaval  (pre-kaf-mil}.     Pertaining  to  the  precava;  the  anterior  caval 

vein,  formerly  called  the  superior  vena   cava,  or  vena  cava   de- 

scendens. 

Pronation  (pro-na'-shun^).      The  turning  of  the  palm  downward. 
Protoplasm  (pro'-to-plazm).     An  albuminous  substance,  ordinarily  re- 

sembling the  white  of  an  egg,  consisting  of  carbon,  oxygen,  nitro- 

gen, and  hydrogen  in  extremely  complex  and  unstable  molecular 

combination,  and  capable,  under  proper  conditions,  of  manifesting 

certain  vital  phenomena,  such  as  spontaneous  motion,  sensation, 

assimilation,  and  reproduction,  thus  constituting  the  physical  basis 

of  life  of  all  plants  and  animals. 
Ptyalin  (tl'-a-lin}.     An  amylolytic  or  diastasic  ferment  found  in  saliva, 

having  the  property  of  converting  starch  into  dextrin  and  sugar. 
Pulmonary  (pul'-mo-na-ri).     Pertaining  to  the  lungs. 
Pylorus  (pi-lo'-rus).     The  opening  of  the  stomach  into  the  duodenum. 
Radius  (ra'-di-us).     The  outer  of  the  bones  of  the  forearm. 
Renal  (re'-naV).     Pertaining  to  the  kidneys. 
Rennin  (ren'-w).     An  enzyme,  or  ferment,  to  whose  action  is  due  the 

curdling  or  clotting  of  milk  produced  upon  the  addition  of  ren- 

net. 
Retina  (ret'-i-na}.     The  chief  and  essential  peripheral  organ  of  vision; 

the  third  or  internal  coat  or  membrane  of  the  eye,  made  up  of  the 

end  organs  or  expansion  of  the  optic  nerve  within  the  globe. 


GLOSSARY.  369 

Sacrum  (sa'-kruni).     A  curved  triangular  bone,  composed  of  five  con- 
solidated vertebrae,  wedged  between  the  two  iliac  (pelvic)  bones, 

and  forming  the  dorsal  boundary  of  the  pelvis. 
Scapula  (skap'-u-la).     The  shoulder-blade. 
Sciatic  (si-at'-ik}.     Pertaining  to  the  ischium;  the  sciatic  nerve,  the 

main  nerve  of  the  thigh. 
Sclerotic  (skle-rot'-ik).     Hard,  indurated;  pertaining  to  the  outer  coat 

of  the  eye. 
Semilunar  (sem-i-lu'-nar}.     Resembling  a  half-moon  in  shape;  semilu- 

nar  valves,  pocket-like  valves  at  the  beginning  of  the  aorta  and 

pulmonary  artery. 
Serous  (se'-rus).     Pertaining  to,  characterized  by,  or  having  the  nature 

of,  serum. 
Serum  (se'-rum*).     The  yellowish  fluid  separating  from  the  blood  after 

the  coagulation  of  the  fibrin. 

Solar  plexus  (so'-lar).     Solar,  with  radiations  resembling  the  sun. 
Sphincter  (sfinyk'-ter'),     A  muscle  surrounding  and  closing  an  orifice. 
Splenic  (splen'-ik).     Pertaining  to  the  spleen. 
Steapsin  (s£ep'-,sm).     A  diastasic  ferment  which  causes  fats  to  combine 

with  an  additional  molecule  of  water  and  then  split  into  glycerine 

and  their  corresponding  acids. 
Sternum  (ster'-num}.     The  breast-bone. 
Subclavian  (sub-kla'-vi-an).     Situated  under  the  collar-bone  ;    subcla- 

vian  artery  and  vein. 
Sublingual  (sub-ling1 '-ywal).     Lying  beneath  the  tongue,  as  sublingual 

gland. 
Submaxillary  (sub-mak '-si-la-ri}.     Lying  beneath  the  lower  maxilla,  as 

submaxillary  salivary  gland. 

Supination  (su-pi-na'-shun}.     The  turning  of  the  palm  upward. 
Synovia  ($i-no'-vi-a).     The  lubricating  liquid  secreted  by  the  synovial 

membranes  in  the  joints. 

Tarsus  (£ar'-sws).     The  instep,  consisting  of  seven  bones. 
Temporal  (tem'-po-ral).     Pertaining  to  the  temples,  as  temporal  artery, 

vein,  muscle,  etc. 
Tetanus  (tet'-a-nus}.     A  spasmodic  and  continuous  contraction  of  the 

muscles,  causing  rigidity  of  the  parts  to  which  they  are  attached. 
Thein  (the'-in).     An  alkaloid  found  in  tea. 

Theobromin  (Mr-o-bro'-mm).     A  feeble  alkaloid  obtained  from  cacao- 
butter  ;  the  essential  substance  found  in  cocoa  and  chocolate. 


37O  GLOSS  A  A'\' 

Thyroid  (thi'-roid).  Shield-shaped,  as  the  thyroid  cart ilage  of  the 
larynx. 

Tibia  (tib'-i-a).  The  larger  (inner)  of  the  two  hones  of  tin-  leg,  com- 
monly called  the  shinbone. 

Trachea  (tra-ke'-a  or  tra'-kc-it).     The  windpipe. 

Triceps  (tri'-seps).  Triceps  of  the  arm,  the  extensor  of  the  arm.  lyinu 
along  the  back  of  the  humerus. 

Tricuspid  (trl-kim'-piil).  Having  three  cusps  or  points,  as  the  trienspid 
valve. 

Trypsin  (trip'-sin}.     The  proteolytic  ferment  of  pancreatic  juice. 

Ulna  (ul'-na).     The  larger  (inner)  of  the  two  bones  of  the  forearm. 

Ureter  (fi-re'-ter).  The  tube  conveying  the  urine  from  the  pelvis  of  the 
kidney  to  the  bladder. 

Vaso-constrictor  (rr/.x'-o-A-on-N/r/A-'-f  <>/•).  Causing  a  constriction  of  the 
blood-vessels. 

Vaso-dilator  («a*'-d-cK4a/-tor).  Pertaining  to  the  positive  dilating  mo- 
tility  of  the  non-striated  muscles  of  the  vascular  system. 

Vaso-motor  (vas-o-ino'-tor).  Serving  to  regulate  the  tension  of  the 
blood-vessels,  as  vaso-motor  nerves  ;  including  vaso-dilator  and 
vaso-constrictor  mechanisms. 

Ventricle  (ven'-tri-kl).  Applied  to  certain  structures  having  a  bellied 
appearance.  The  cavities  of  the  heart  from  which  the  blood  is 
forced  out  through  the  arteries. 

Vesicle  (ves'-i-kl}.  A  small,  membranous,  bladder-like  formation,  as 
air  vesicle. 

Villus  (wT-its),  pi.  villi.  One  of  the  numerous  minute  vascular  projec- 
tions from  the  mucous  membrane  lining  the  small  intestine,  for  ab- 
sorbing digested  food. 

Vitreous  O*T-re-w«).  Glass-like,  as  the  clear,  jelly-like,  vitreous  humor 
of  the  eye. 


INDEX. 


Abdomen,  cross  section  of,  i6f. 
Abdominal  respiration,  95. 
Absorption,  181. 

Of  fats,  182,  183. 

From  stomach,  175. 
Accommodation,  291. 
Acids,  indigestion,  179. 

Fatty,  179. 

In  poisoning,  323. 

Tasting,  302. 
Action  of  large  arteries,  49. 

Of  gullet,  171. 

Of  heart,  45  ;  rhythmic,  65. 

Of  diseased  kidneys,  197. 

Of  muscle,  9. 

Of  ciliary  muscle,  291. 

Reflex,  30,  32,  263. 
Adam's  apple,  309. 
Adjustment  of  lens,  290. 
Afferent  currents,  268. 

Nerve  fibers,  27,  28,  32. 

Nerve  roots,  33,  31. 
After-images,  295. 

Negative,  295 ;  Positive,  295. 
After-pressure,  281. 
Air,  complemental,  96,  97. 

Composition  of,  100. 

Currents  about  stoves,  116. 

Expired,  102. 

Reserve,  96,  97. 

Residual,  96,  97. 

Sacs,  84,  91. 

In  the  sickroom,  325. 

Tidal,  96,  97. 

Vesicles,  84,  91,  103. 

Washed,  119. 
Albinos,  288. 
Albumen,  145. 


Albuminuria,  199. 
Alcohol,  208. 

In  the  army,  216,  217. 

Binz,  218. 

Brunton,  250. 

And  circulation,  70. 

Clum,  252. 

And  cold  climates,  209. 

And  crime,  208. 

Crothers,  251. 

Effects  of,  210,  223. 

And  energy,  208,  212. 

And  excesses,  252. 

Greely,  216. 

Halliburton,  222. 

And  heat,  209. 

Hornaday,  221. 

Howell,  212. 

Luce,  260. 

Martin,  253. 

M'Kendrick,  222. 

Miura,  213. 

Moral  deterioration,  253. 

As  a  narcotic,  210. 

And  nerve  centers,  251. 

And  nervous  system,  250. 

As  a  poison,  210. 

Reichert,  213. 

Rohe,  218. 

Stanley,  216. 

Stevenson  and  Murphy,  250. 

As  a  stimulant,  210. 

Thompson,  214. 

And  training,  209. 

In  the  tropics,  221. 

And  water,  210. 

Woodhull,  216. 

Woodruff,  217. 


371 


372 


INDEX. 


Alcoholic  beverages,  218. 
Alkalies,  in  digestion,  179. 

In  poisoning,  323. 
Alveoli,  of  the  lungs,  84. 
Ameba,  5. 
Amount  of  blood,  75. 

Of  food  needed,  193. 

Of  perspiration,  136. 

Of  saliva,  168. 
Amylopsin,  178. 
Anabolism,  203. 
Anatomy  defined,  3. 

And  sculpture,  346. 
Anesthetics,  254. 
Animal  matter,  338,  339. 

Protoplasm,  202. 
Animals  and  plants,  205. 
Antidotes  to  poisons,  322,  347. 
Aorta,  44,  177. 
Apex  beat  of  heart,  49. 
Apoplexy,  248. 
Appendicular  skeleton,  330. 
Appendix,  vermiform,  187. 
Aqueous  humor,  288,  289. 
Arch,  neural,  330,  331. 
Aristotle's  experiment,  266. 
Arm,  bleeding  from,  314. 
Arrangement  of  teeth,  164. 

Of  muscles,  341, 

Arterial  muscle,  exercise  of,  233. 
Arteries,  large,  action  of,  49. 

Bleeding  from,  314. 

Distribution  of,  44. 

And  exercise,  69. 

Regulation  of  size,  68. 

Structure  of,  51. 
Artery,  carotid,  44,  314. 

Gastric,  44. 

Hepatic,  44,  177. 

Iliac,  44. 

Mesenteric,  177. 

Pancreatic,  44. 

Pulmonary,  42,  43. 

Renal,  44. 

Splenic,  44. 

Subclavian,  44. 
Articulating  process,  331. 
Articulations  of  vertebra,  335. 
Artificial  life,  i. 

Renewal  of  air,  116. 


Auditory  center,  244,  264. 

Nerve,  239,  238,  305. 
Auricles  of  heart,  41,  47. 

Contraction  of,  46. 
Asiatic  cholera,  Bacillus  of,  123. 
Association  fibers,  264. 
Astigmatism,  292. 
Atlas,  335. 
Axial  skeleton,  330. 
Axis,  335 ;  axis  cylinder,  27,  28. 

Bacilli,  types  of,  123. 

Bacillus,  of  Asiatic  cholera,  123. 

Of  diphtheria,  123. 

Of  hog  cholera,  123. 

Tuberculosis,  122,  123 

Of  typhoid  fever,  123. 
Bacteria,  124. 

Of  putrefaction,  127. 
Baking  meat,  156. 

Powder  bread,  189. 
Ball  and  socket  joint,  339. 
Bandaging,  328. 
Barley,  149. 
Baseball,  229. 
Bathing,  232. 

The  sick,  326;  Time  for,  233. 
Bath  mils.  232. 
Baths,  cold,  232;  warm,  233. 
Beans,  dried,  189. 
Bear,  hibernation  of,  201. 
Bedding,  changing  in  sickroom.  326. 
Bee-stings,  324. 
Beef  extract,  155. 

Tea,  155. 
Beets,  189. 

Beverages  containing  alcohol,  218. 
Biceps,  8,  15. 
Bicuspid  teeth,  164. 
Bicycling,  230. 
Bile,  177. 

Duct,  186,  177. 

Functions  of,  178. 

Sac,  160,  186. 

Bites  of  cats,  324;  dogs,  324;  snakes,  324. 
Bitters,  taste  of,  302. 
Blackberries,  189. 

Bleeding  from  arm,  314;    arteries,  314; 
neck,  314;  nose,  315;  veins,  315. 
Blind  spot,  293. 


INDEX. 


373 


Blindness,  color,  295. 

Blister,  132. 

Blood,  amount  of,  75. 

Changes  in,  106. 

Chemical  reaction  of,  75. 

Coagulation  of,  74. 

Color  of,  73. 

Composition  of,  71. 

Of  frog,  73. 

Gases  of,  104. 

And  glands,  134. 

Mixture  of  good  and  bad,  196. 

Quantity  in  different  organs,  75. 

Renewal  of,  200. 

And  river,  195. 

Specific  gravity  of,  75. 

Transfusion  of,  81. 

Work  of,  39. 
Blood-flow,  and  exercise,  107. 

And  lymph-flow,  77,  78. 

Rate  of,  59. 

Blood-pressure,  of  ventricle,  46. 
Blood-stream  and  sewer,  199. 
Blood-supply  of  brain,  247. 

Of  stomach,  173. 
Blood-tubes  joining  heart,  42. 
Blowing,  96. 
Blushing,  68. 
Boats  upsetting,  321. 
Body,  care  of,  2. 

And  locomotive,  109. 

Temperature  of,  108. 
Boiled  milk,  189. 

Boiling  meat,  156 ;  boiling  water,  152. 
Bone,  composition  of,  338. 

Corpuscles,  337. 

Lamellae  of,  337. 
Bone,  structure  of,  18,  337. 
Bones,  broken,  317. 

Of  ear,  305,  306. 

Hygiene  of,  339. 

Lightness  and  strength  of,  20. 

Relation  to  muscles,  15. 

Table  of,  333. 

Uses  of,  21,  330. 

Weight  of,  337. 
Bow-legs,  339. 
Boxing,  229. 
Brain,  235. 

Blood-supply  of,  247. 


Brain  centers,  connection  of,  263. 

Convolutions  and  intelligence,  240. 

Ganglia  of,  241. 

Gray  matter  of,  241. 

Hemispheres  of,  240. 

Location  of  functions,  244. 

Parts  of,  235. 

Preservation  of,  236. 

Rest,  246,  247. 

And  sensation,  30,  243. 

The  water-cushion  of,  248. 

White  matter  of,  241. 

Work,  246. 
Bread,  hot,  189. 
Breathing,  effect  on  circulation,  98. 

Deep,  97,  98. 

Hygiene  of,  97. 

Through  mouth,  98. 

Restoring,  320. 

And  swallowing,  170,  171. 
Broiling  meat,  156. 
Broken  bones,  317. 
Bronchi,  43. 
Bruises,  340. 
Bulb,  hair,  130. 

Olfactory,  303. 

Spinal,  245,  246. 
Burning  clothing,  316. 
Burns,  treatment  of,  316. 

Cabbage,  189. 

Caffein,  155. 

Cake,  189. 

Calf  muscle  of  frog,  9. 

Camel's  hump,  201. 

Canaliculi,  338. 

Canals,  haversian,  337,  338. 

Canals,  semicircular,  305,  306. 

Candle,  heat  of,  205. 
And  respiration,  201. 

Cane  sugar,  179. 

Canine  teeth,  164. 

Capacity  of  lungs,  97,  96. 
Vital,  97. 

Capillaries,  blood-flow  in,  55  ;  of  frog's 
web,  52,  53  ;  of  lung,  91  ;  of 
muscle,  54 ;  pulmonary,  86. 

Capsule  of  lens,  289. 

Carbohydrate  food,  147. 

Carbohydrates,  147. 


374 


Carbon  dioxid  of  air,  100,  102;  in  blood, 
i<xj ;   in  bivatli,  102;   in  wells,  322. 
Care  of  body,  importance  of,  2. 

Of  ears,  307. 

Of  eyes,  295. 

Of  lamps  in  sickroom,  328. 

Of  the  sick,  324,  325. 

Of  teeth,  166. 
Carotid  artery,  44,  314. 
Carpal  bones,  333. 
Carpus,  332,  333. 
Cartilage,  19. 

Cricoid,  309. 

Intervertebral,  335. 

Thyroid,  309. 
Cartilages  of  windpipe,  86. 
Casein,  144,  145. 
Cataract,  293. 
Cats,  bites  from,  324. 
Cauliflower,  189. 
Cauterizing,  324. 
Cavities,  lymph,  80. 

Serous,  80. 

Of  skeleton,  337. 
Cavity,  pulp,  163,  164. 
Cecum,  1 86. 
Celery,  189. 
Cells,  aquatic,  79. 

Ciliated,  86. 

Division  of,  5. 

Of  epidermis,  53. 

Epithelial,  4. 

Fat,  130. 
Cells  and  lymph,  79,  200. 

Muscle,  5,  345. 

Nerve,  5,  28. 

And  oxygen,  107. 

Pigment,  52,  53. 

Poisoning  of,  200. 

Starvation  of,  200. 

Structure  of,  4. 
Center  of  control  of  circulation,  68. 

For  hearing,  244,  264. 

Respiratory,  99. 

Of  sensation,  243,  245. 

For  speech,  245,  264. 

For  vision,  264. 
Centrum,  330. 
Cerebellum,  236,  245. 
Cerebral  cortex,  functions  of,  243. 


Cerebro-spinal  system,  cat,  26. 

Of  man,  24,  25. 
Cerebrum,  235,  241. 
Cervical  vertebrae,  332,  333. 
Cesspools,  151. 
Change  of  voice,  313. 
Cheese,  147,  189,  191. 
Chemical  composition  of  bone,  338. 
Chemistry  of  respiration,  too. 
Children,  exercise  of,  228. 
Chloral  hydrate,  257. 
Chloroform,  257. 
Chocolate,  155,  189,  212. 
Choking,  96. 
Cholera,  Asiatic,  bacillus  of,  123. 

Hog,  bacillus  of,  123. 
Choroid  coat,  287. 
Churning  in  the  stomach,  174. 
Chyle,  receptacle  of,  184,  186. 
Chyme,  175. 

Cider,  212;  fermentation  of,  121,  212. 
Cigarettes,  259. 
Cigars,  258. 
Cilia,  87. 
Ciliary  muscle,  290,  291. 

Process,  288. 
Ciliated  cells,  86. 
Circulation  and  alcohol,  70.    . 

Control  of,  64. 

Diagram  of,  60,  196,  197,  198. 

In  frog's  web,  52,  53,  54. 

In  gray  matter,  249. 

In  muscle,  54. 

Plan  of,  60. 

Portal,  177. 

In  white  matter,  249. 
Circumvallate  papillae,  302. 
Classification  of  senses,  271. 
Clavicle,  332,  333. 
Cleanliness  of  eyes,  298. 
Climate  and  alcohol,  209. 
Clothing,  regulating  heat,  138. 

Effect  of  wet,  139. 
Coagulation  of  blood,  74. 

Of  muscle  plasma,  346. 
Coat,  choroid,  287. 

Sclerotic,  287. 

Coats  of  eye,  287 ;  of  stomach,  172. 
Cocaine,  257. 
Coccyx,  332,  333,  335. 


INDEX. 


375 


Cochlea,  305,  306. 
Cocoa,  155,  189. 
Coffee,  155,  189,  212. 
Cold  baths,  232. 

Spots,  283. 

Taking,  231. 
Colds  and  deafness,  307. 
Colon,  187. 
Color  blindness,  295. 

Of  blood,  73,  105. 

Sensations,  294. 

Of  skin,  132. 
Colored  corpuscles,  71. 
Colorless  corpuscles,  72. 

As  germ  destroyers,  126. 
Column,  spinal,  334. 
Common  sensations,  272. 
Compass  points  and  touch,  281. 
Complemental  air,  97. 
Composition  of  air,  100. 

Of  blood,  71. 

Of  bone,  338. 

Of  sweat,  135. 
Conduction  of  heat,  137. 
Cones  and  rods,  293,  292. 
Conjunctiva,  286. 
Connective  tissue,  n,  12. 
Consciousness,  243. 
Conservation  of  energy,  206. 
Consonants  and  vowels,  312. 
Constipating  foods,  189. 
Constipation,  178,  188. 
Consumption,  danger  from,  122. 
Contraction  of  auricle,  46. 

Of  ventricle,  46. 
Control  of  diaphragm,  100. 

Of  mind,  247. 

Of  respiration,  99. 
Convalescence  and  reading,  298. 
Convection  of  heat,  137. 
Conversation  at  meals,  192. 
Convolutions  of  brain,  235,  240. 

And  intelligence,  240. 
Convulsions,  346. 
Cooking,  155. 
Coordination,  245. 

Cord,  spinal,  24 ;  reflex  action  of,  30,  32. 
Cords,  tendinous,  41,  46 ;  vocal,  309. 
Corn,  148,  189. 
Cornea,  288. 


Corpuscles  of  blood,  72,  53. 

Bone,  337. 

Colored,  71,  72,  104. 

Colorless,  72,  126. 

Touch,  279. 

Correlation  of  energy,  206. 
Cortex,  cerebral,  functions  of,  243. 
Coughing,  95. 

Covering  of  brain,  235  ;  of  heart,  40. 
Cracked  wheat,  189. 
Crackers,  189. 
Cramps,  35. 

Cranial  nerves,  237,  242. 
Cream,  144. 
Cricoid  cartilage,  309. 
Crime  and  alcohol,  208. 
Crossing  of  nerve  fibers,  35,  243. 
Crown  of  tooth,  163. 
Crying,  95. 

Crystalline  lens,  288,  289. 
Culture  of  voice,  313. 
Curdling  in  stomach,  174. 
Currents,    afferent,    268,    269;     efferent, 

268;  induction,  266. 
Curvature  of  spine,  339. 
Custard,  189. 

Cutaneous  sensations,  278. 
Cylinder,  axis,  27. 

Danger  of  consumption,  122. 

Dead  dust,  119. 

Deafness  and  colds,  307. 

Deep  breathing,  99. 

Defects  in  eyesight,  291. 

Deliberation  in  eating,  192. 

Dental  formula,  164. 

Dentine,  163,  164. 

Dermis,  132. 

Desserts,  191. 

Dextrose,  179. 

Diabetes,  199. 

Dialysis,  182. 

Diaphragm,  85,  87,  88,  177,  344. 

Control  of,  99. 
Diarrhea,  231. 
Diastole,  47. 

Diet,  errors  of,  193;    mixed,  153;    one- 
sided, 153;  proper,  154. 
Diffusion  of  gases,  115;  of  liquids,  182. 
Digestion,  hygiene  of,  190. 


3/6 


Digestion,  organs  of,  160. 

Outline  of,  187. 

Time  in  stomach,  175. 
Digestive  tube,  159. 
Dilation  of  ventricle,  47. 
Diphtheria,  bacillus  of,  123. 
Direct  heating,  118. 
Disease  germs,  122. 

Of  lungs,  126. 

Prevention  of,  126. 
Dislocations,  339. 
Distribution  of  arteries,  44 ;  of  veins,  44. 

Of  heat,  138. 
Division  of  cells,  5. 

Of  labor,  physiological,  4. 
Dogs,  bites  from,  324. 
Double  windows,  119. 
Dreams,  266. 
Dried  fish,  189. 
Drink,  hot,  191. 
Drinking,  96. 

Water,  152. 
Dropsy,  80. 

Drowned,  treatment  of,  317. 
Drowning,  resuscitation  from,  317. 
Duodenum,  160. 
Dura  mater,  235. 
Dust,  avoiding,  124. 

Dead,  119;  live,  121. 

And  lungs,  120. 

Sources  of,  120. 
Dusting,  125. 

Ear,  bones  of,  305,  306. 

Care  of,  307. 

External,  305. 

Internal,  306. 

Middle,  305. 

Parts  of,  305. 

Use  of,  307. 
Eating  between  meals,  193. 

Deliberation  in,  192. 

Time  of,  193. 
Eddy,  living,  199. 
Efferent  nerve  currents,  268. 

Nerve  fibers,  27,  32,  33. 
Eggs,  146. 
Electric  light,  296. 
Emetic,  mustard,  323. 
Emulsion,  147,  179. 


Enamel,  163,  164. 
Energy  and  alcohol,  208. 

Conservation  of,  206. 

Correlation  of,  206. 

From  food,  204. 

Utilization  of,  205. 
Ennui,  95. 

Entire  wheat  flour,  148. 
Enzymes,  169. 
Epidermis,  53,  131. 
I  Epiglottis,  170,  171,  310. 
Epithelial  cells,  4. 
Equilibrium  sense,  306. 
Errors  in  diet,  193. 
Essentials  of  reflex  action,  32. 
Ethmoid  bone,  333. 
Eustachian  tube,  306,  305,  170,  171. 
Evaporation  of  sweat,  137. 
Evening  reading,  297. 
Excretion,  130;  of  urea,  202. 
Exercise  of  arterial  muscles,  233. 

And  bathing,  226. 

And  blood-flow,  107. 

Forms  of,  228. 

And  health,  226. 

And  heat,  137. 

And  long  life,  227. 

And  size  of  arteries,  69. 
Expiration,  elastic  reactions  of,  94. 
Explosion  in  muscles,  no. 
Expression,  muscles  of,  345. 
Extensor  muscle,  8. 
External  ear,  305. 
Extract  of  beef,  155. 
Eye,  coats  of,  287. 

Dissection  of,  287. 

External  parts  of,  286. 

Movements  of,  287. 

Muscles,  286,  288. 

Protection  of,  285. 

Section  of,  288. 

Structure  of,  288. 
Eyes,  of  albinos,  288. 

Care  of,  295. 

Cleanliness  of,  298. 

Irritation  of,  298. 

Pain  in,  294. 

Pigment  in,  288. 

Resting,  297. 

Sympathy  between,  294. 


INDEX, 


377 


Eyeball,  muscles  of,  286. 
Eyeglasses,  292. 
Eyesight,  defects  of,  291. 
Eyestrain,  299. 

Facial  expression,  345. 

Nerves,  238. 
Fainting,  316,  248. 
Fans,  ventilating,  117. 
Far-sight,  291,  292. 
Farina,  189. 
Fat  cells,  130. 

And  muscles,  346. 

As  a  tissue,  201. 
Fats,  147. 
Fatty  acids,  179. 

Fatigue,  246,  272 ;  from  standing,  268. 
Femur,  18,  332,  333. 
Fever,  typhoid,  151. 
Fiber,  muscle,  plain,  50,  344. 

Muscle,  striated,  n,  12,  344. 

Nerve,  28. 

Fibers,  association,  264. 
Fibrin,  74,  145. 
Fibula,  333. 
Filiform  papillae,  301. 
Fish,  146;  dried  fish,  189. 
Flavors,  302. 

Flexibility  of  spinal  column,  335. 
Flexion  of  forearm,  16. 
Flexor  muscle,  8,  13. 
Flexure,  sigmoid,  188. 
Floating,  321. 

Flour,  entire  wheat,  148;  Graham,  148. 
Flow  of  lymph,  77. 
Flues,  ventilating,  115. 
Food,  amount  needed,  193. 

Object  of,  159. 

Regulating  temperature,  138. 

For  the  sick,  327. 

Source  of  energy,  204. 
Foods,  144. 

Constipating,  189 ;  laxative,  189. 

Preservation  of,  127. 
Foodstuffs,  144,  145. 
Foot  asleep,  37 ;  as  kind  of  lever,  17. 
Football,  229. 

Force,  indestructibility  of,  204. 
Forced  respiration,  94. 
Forms  of  exercise,  228  ;  of  muscles,  341. 


Formula,  dental,  164. 
Foul  air  shafts,  117. 
Frog,  blood  of,  73. 

Without  cerebrum,  241. 

Muscle  action  of,  9. 
Frontal  bone,  332,  333. 
Fruits,  150. 

Acid,  189. 

Pies,  189. 

Puddings,  189. 
Frying,  156. 
Fulcrum,  16. 
Function,  defined,  3. 

Of  cerebellum,  245. 

Of  cerebral  cortex,  243. 

Of  cerebrum,  241. 

Of  nerve  fibers,  28. 

Of  nerve  roots,  33. 

Of  skin,  136. 

Of  spinal  bulb,  245. 

Of  spinal  cord,  29. 
Fungiform  papillae,  301. 
Furnaces,  117. 

Gain  and  loss  of  body,  195. 
Game,  wild,  189. 
Games  of  children,  228. 
Ganglia,  29;  of  brain,  241. 

Sympathetic,  65. 
Ganglion  of  dorsal  root,  26,  29. 
Gargling,  95. 
Gases  of  blood,  104. 

Diffusion  of,  115. 

Gastric  glands,  173 ;  juice,  173,  174. 
Gelatin,  145. 

General  sensations,  271,  272. 
Germs  of  disease,  122. 
Glands  and  blood  supply,  134. 

Compound,  133. 

Essentials  of,  134. 

Gastric,  173. 

Intestinal,  176. 

Lacrymal,  286. 

Lymphatic,  77,  183. 

Mucous,  169. 

Oil,  130. 

Salivary,  166. 

Simple,  133,  135. 

Sweat,  133. 
Glasses,  wearing,  299. 


3/8 


INDEX. 


Gliding  joints,  339. 
Glossopharyngeal  nerves,  239. 
Glottis,  170,  171. 
Gluten,  145. 
Glycogen,  178,  202. 
Graham  flour,  148. 
Grains,  147. 
Granula,  189. 
Grape  sugar,  179. 
Grates  as  ventilators,  114. 
Gravity  and  circulation,  61. 
Gray  matter  of  brain,  241. 

Matter,  circulation  in,  249. 

Matter  of  spinal  cord,  28,  29,  31. 
Gray  nerve  fibers,  28. 
Gullet,  160,  170,  171,  186. 

Habit,  212. 

Acquired  reflex  action,  267. 
Hair,  130, 133 ;  bulb,  130. 
Hammer  bone,  333. 
Hard  palate,  170. 
Harmony  in  muscle  action,  21,  36. 
Hauser,  Kaspar,  271. 
Haversian  canals,  337. 
Hawking,  95. 

Headaches  from  eyestrain,  299. 
Health,  i. 
Hearing,  304. 
Heart,  action  of,  45  ;  rhythmic,  64. 

Auricles  of,  41,  46. 

Beat  of,  39,  49. 

Blood  tubes  joining,  42. 

Covering,  40. 

Dissection  of,  42. 

Muscle,  344. 

Nourishment  of,  61. 

Position  of,  40. 

Size  of,  41. 

Sounds  of,  49. 

Structure  of,  41. 

Valves  of,  41. 

Ventricles  of,  41,  46. 

Work  and  rest  of,  48. 
Heat  and  alcohol,  209. 

Conduction  of,  137. 

Convection  of,  137. 

Distribution  of,  138. 

And  exercise,  137. 

From  oxidation,  109. 


Heat,  production  of,  106. 

Radiation  of,  137. 

Ways  of  giving  off,  137. 
Heating,  direct,  118;  indirect,  118. 
Hemispheres  of  brain,  235,  240. 
Hemoglobin,  74,  104. 
Hemorrhage  of  lungs,  315. 

Of  stomach,  315. 

Hepatic  arteries,  177 ;  veins,  177,  186. 
Hibernation,  201. 
Hiccuping,  95. 
Hinge  joint,  339. 
Hoarseness,  313. 
Hog  cholera,  bacillus  of,  123. 
Hope  in  illness,  325. 
Hot  drink,  191. 
Humerus,  332,  333. 
Humor,  aqueous,  288,  289. 

Vitreous,  288,  289. 
Hump,  camel's,  201. 
Hunger,  276. 
Hyaloid  membrane,  289. 
Hygiene  of  bones,  339. 

Of  breathing,  97. 

Defined,  3. 

Of  digestion,  190. 
Hyoid  bone,  333. 
Hypoglossal  nerve,  240. 

Ice  water,  152. 

Ignoring  nerve  currents,  266. 
Iliac  arteries,  44 ;  veins,  44. 
Image,  inversion  of,  290. 
Immovable  joints,  339. 
Importance  of  retina,  293. 
Impulse,  nerve,  28,  36. 

Transmission  of,  36. 
Impurities  in  water,  151. 
Incisor,  164. 
Incus,  333. 
Indestructibility  of  force,  204. 

Of  matter,  203. 
Indirect  heating,  118. 
Induction  current,  266. 
Inebriety,  Clum,  260;  Crothers,  260. 

A  disease,  253. 

Palmer,  260. 
Inhibition,  67. 
Innominate  bones,  333. 
Insertion  of  muscle,  10,  15. 


INDEX. 


379 


Inspiration,  91 ;   and  expiration,  92. 

Forces  of,  94. 

Resistances  to,  94. 

Intelligence,  243;  and  convolutions,  240. 
Interference  with  reflex  action,  35. 
I ntervertebral  cartilages,  335. 
Intestine,  176,  177. 

Large,  186,  188 ;  small,  160,  176,  186. 
Intestinal  glands,  176, 179. 
Inversion  of  image,  290. 
Invertin,  179. 
Iris,  288. 

Iron,  in  blood,  74. 
Irritant  poisons,  323. 
Irritation  of  eye,  298. 
Ivy  poisoning,  324. 

Jacketed  stoves,  117. 
Joints,  19,  339. 
Judgment,  266. 
Jugular  vein,  44. 
Juice,  gastric,  173. 

Intestinal,  179. 

Lime,  150. 

Pancreatic,  177. 

Kaspar  Hauser,  271. 
Katabolism,  203. 
Kidneys,  139. 

Diseased,  197. 

And  skin,  141,  142. 
Kinds  of  teeth,  164. 

Labor,  physiological  division  of,  4. 
Lacrymal  bone,  333 ;  gland,  286. 
Lacteals,  181,  184,  186. 
Lacunoe  of  bone,  337. 
Lamellae,  of  bone,  337. 
Lamps,  in  sickroom,  328. 
Larynx,  from  above,  311. 

Structure  of,  310. 
Lateral  process,  331. 
Laughing,  95. 
Laxative  foods,  189. 
Leather,  132. 
Ledger  of  body,  195. 
Legumin,  145. 
Lens  capsule,  289. 

Crystalline.  288,  289. 


Levers,  16,  17. 

Life,  artificial,  i ;  natural,  I. 

Processes,  203. 
Ligament,  suspensory,  288. 
Ligaments,  19. 
Light,  electric,  296. 

In  sickroom,  325. 

Strength  of,  297. 
Lingering  of  sensations,  267. 
Live  dust,  121. 
Liver,  177,  160. 

As  food,  189. 

Position,  85. 

Starch,  178. 
Lobes,  olfactory,  237. 
Local  sign,  281. 

Location  of  brain  functions,  244. 
Locomotion,  19;  by  reaction,  20. 
Loss  and  gain  of  body,  195. 
Loudness  of  voice,  311. 
Lumbar  vertebrae,  332,  333,  335. 
Lung  diseases,  126. 
Lungs,  87. 
.    Parts  of,  84. 

Capacity  of,  97. 

Dorsal  view  of,  43. 

Hemorrhage  of,  315. 
Lymph,  79. 

Cavities,  80. 

Flow  of,  77. 

Importance  of,  80. 

Renewal  of,  200. 

Spaces,  75. 

Tubes,  76. 

Variations  in,  80. 
Lymphatic  glands,  77,  183. 
Lymphatics,  183,  184. 

Malar  bone,  333. 

Malleus,  333. 

Malted  milk,  155. 

Massage,  81. 

Masseter  muscle,  8. 

Mastication,  imperfect,  192. 

Matter,  animal,  in  bone,  338, 339. 

Indestructibility  of,  203. 

Mineral  in  bone,  338,  339. 
Maxilla,  inferior,  333. 

Superior,  333. 
Meals,  conversation  at,  192. 


INDEX. 


Meat,  146;   baking,  1^6;    boiling,  156; 
broiling,  156 ;  roasting,  156 ;  salted, 
189 ;  smoked,  189. 
Mechanism,  of  body,  2. 
Media,  refracting  of  eye,  289. 
Medullary  sheath,  27. 
Membrane,  hyaloid,  289. 
Memory,  267. 
Meningitis,  248. 
Mesentery,  161,  186. 
Mesenteric  artery,  177 ;  vein,  186. 
Metabolism,  203. 
Metacarpus,  333,  334. 
Metatarsal  bones,  333. 
Metatarsus,  332,  333. 
Middle  ear,  305. 
Milk,  144,  146. 

Boiled,  189;  Malted,  155. 

Souring  of,  127. 

Teeth,  164. 
Mind,  control  of,  247. 
Mineral  matter  in  bone,  338,  339. 
Mitral  valve,  41. 
Mixed  diet,  153. 

Joints,  339. 

Modification  of  respiration,  95. 
Molars,  164. 
Molds,  121. 
Morphia,  255. 
Morphine,  255. 
Motion,  experiments  with,  7. 

Involuntary,  24. 

And  locomotion,  19. 

Production  of,  106. 

Voluntary,  24. 

Mouth,  162 ;  breathing  through,  98. 
Movable  joints,  339. 
Movements  of  eye,  287. 

Of  respiration,  91. 

Mucous  glands,  169;  Membrane,  86,  87. 
Mucus,  169. 
Muscle,  action  of,  9. 

Capillaries  of,  54. 

Explosion  in,  no. 

Insertion  of,  10,  15. 

Normal  condition  of,  13. 

Origin  of,  10,  15. 

Shortening,  13,  24. 

Structure  of,  10,  n. 
Muscle-action,  harmony  in,  36. 


Muscle-action,  laws  of,  12. 
Muscle-cells,  5,  345;  of  heart,  344. 
Muscle-fiber,  a  cell,  345. 
Muscle-fibers  compared,  344. 

Plain,  in  artery,  50. 

Plain  and  striated,  52,  344. 

In  lymph  tubes,  77. 
Muscle-plasma,  coagulation  of,  346. 
Muscles,  arrangement  of,  341. 

Arterial,  exercise  of,  233. 

Biceps,  8. 

Ciliary,  290,  291. 

Of  expression,  345. 

Of  eyeball,  286,  288. 

And  fat,  346. 

Forms  of,  341. 

Importance  of,  12. 

Names  of,  344. 

Number  of,  341. 

Papillary,  46. 

Relation  to  bone,  15. 

Size  of,  341. 

Skeletal,  15. 

Sphincter,  175. 

Superficial,  342,  343. 

Symmetrical  development  of,  14. 

Temporal,  9. 

Triceps,  8. 
Muscular  exertion  and  urea,  202. 

Power,  loss  of,  37. 

Sense,  272. 

Sense  and  sight,  274. 
Myosin,  145. 

Nails,  133. 

Rusty,  wounds  from,  323. 
Names  of  muscles,  344. 
Narcosis,  254. 
Narcotics,  254,  257. 
Nasal  bones,  333. 
Nature,  punishments,  i,  227. 

Of  sensation,  264. 
Nausea,  272. 
Near  sight,  291,  292. 
Neck,  bleeding  from,  314. 

Of  tooth,  163,  164. 
Negative  after-images,  295. 
Nerve  cells,  5,  28. 

Centers,  29. 

Currents  afferent  and  efferent,  268, 269. 


INDEX. 


Nerve,  currents  ignoring,  266. 

Endings,  in  skin,  278. 

Fibers,  crossing  of,  35,  243. 

Fibers,  destination  of,  33. 

Fibers,  function  of,  28. 

Fibers,  gray,  28. 

Fibers,  sheath  of,  28. 

Fibers,  similarity  of,  262. 

Fibers,  structure  of,  27,  28. 

Impulse,  28,  36. 

Roots,  functions  of,  33. 

Stimuli,  261. 

Supply  of  heart,  66. 

Supply  of  tongue,  302. 
Nerves,  Auditory,  239,  305. 

Cranial,  237,  242. 

Of  diaphragm,  100. 

Effect  of  pressure,  37. 

Facial,  238. 

Glossopharyngeal,  239. 

Of  hearing,  242,  305. 

Of  heart,  66. 

Hypoglossal,  240. 

Olfactory,  238,  303. 

Optic,  237,  238,  288. 

Pneumogastric  (see  vagus). 

Sciatic  of  frog,  9. 

Of  smell,  303. 

Spinal,  26. 

Structure  of,  27. 

Of  taste,  302,  301. 

Trigeminal,  237. 

Trophic,  251. 

Vagus,  66,  239. 

Vaso-constrictor,  67. 

Vaso-dilator,  67. 

Vaso-motor,  68. 

Nervous  impulse,  nature  of,  28,  36. 
Nervous  system  and  alcohol,  250. 

Cerebro-spinal,  24. 

Sympathetic,  65,  66. 

And  telegraph,  268. 
Nervous  tissue  and  starvation,  247. 
Neural  arch,  330;  ring,  330. 
Neuralgia  and  cold  baths,  233. 
Neuroglia,  241. 
Nicotine,  258. 
Nitrogen  in  air,  100. 
Nose,  bleeding  from,  315. 
Nourishment  of  heart,  61. 


Nucleus,  4;   of  ciliated  cell,  86;  of  epi- 
dermic cell,  53. 
Nurse,  qualities  of,  325. 
Nursing,  325  ;  books  on,  328. 
Nutrition,  202. 
Nuts,  191. 

Oats,  149. 

Occipital  bone,  332.  333. 

Oculist,  consultation  of,  299. 

Odontoid  process,  335. 

Oil  gland,  130. 

Olfactory  bulb,  303,  238,  242. 

Lobes,  237,  242. 

Nerves,  303,  242,  238. 
Onions,  189. 
Opium,  255. 

Optic  nerves,  237,  242,  288,  297. 
Organ,  defined,  3. 
Organs  of  digestion,  160. 

Ledger  account  of,  195. 
Origin,  of  muscle,  10,  15. 
Osmosis,  182. 
Outline  of  digestion,  187. 
Oxidation,  source  of  heat,  109. 

Of  tissues,  107. 
Oxygen  in  the  air,  100. 

Amount  used,  104. 

In  blood,  104. 

Storage  in  tissues,  no. 
Oxy-hemoglogin,  104. 
Oysters,  189. 

Pain,  274;  extent  of,  275. 

In  eyes,  294. 

A  general  sense,  276. 
Palate  bone,  333. 

Hard,  170,  171. 

Sense  of  taste  in,  302. 

Soft,  160,  170,  171. 
Pancreas,  160,  177,  186. 
Pancreatic  duct,  186. 

Juice,  177,  178. 
Panting,  96. 
Papillae,  circumvallate,  303. 

Filiform,  301. 

Fungiform,  301. 

Of  skin,  130,  131,  279. 

Of  tongue,  301. 
Papillary  muscles,  46. 


382 


INDEX. 


Parietal  bone,  332,  333. 

Parotid  salivary  gland,  186. 

Pastry,  189. 

Patella,  332,  333. 

Peaches,  189. 

Peas,  green,  189. 

Pepper,  189. 

Pepsin,  173. 

Peptone,  176. 

Periosteum,  19. 

Peritoneum,  161. 

Perspiration,  130;  amount  of,  136. 

Insensible,  135;  sensible,  135. 
Phalanges,  333,  334. 
Pharynx,  160,  169. 
Physician's  directions,  326. 
Physiology  defined,  3. 
Pia  mater,  235. 
Pie,  191. 

Pigeon  without  cerebrum,  241. 
Pigment  cells,  52,  53. 

Of  eye,  288. 

Of  human  skin,  132. 
Pitch  of  voice,  312. 
Pivot  joint,  339. 

Plain  muscle  fibers,  49,  50,  344. 
Plants,  relation  to  animals,  205. 
Plasma,  73. 
Pleura,  87. 
Plexus,  solar,  66. 
Plums,  189. 
Poison  ivy,  324. 
Poisons,  322,  347. 

Irritant,  323;  neutralizing,  323. 
Pollen,  121. 
Pores,  sweat,  130. 
Portal  circulation,  177;  Vein,  177. 
Positive  after-images,  295. 
Postcaval  vein,  42,  44,  177,  186. 
Potatoes,  149,  189. 
Potential  energy,  in  respiration,  93. 
Poultry,  189. 
Power,  of  levers,  16. 
Precaval  vein,  42,  44,  186. 
Premolars,  164. 
Preservation  of  food,  127. 
Pressure  sense,  280. 

Effect  on  nerves,  37 ;  on  veins,  58. 
Prevention  of  sneezing,  328. 
Process,  articulating,  331 ;  lateral,  331. 


Process,  odontoid,  335. 

Spinous,  331. 

Processes,  of  vertebra,  330. 
Production  of  heat,  106;  of  sound,  306. 
1'ronation,  337. 
Protection  of  eye,  285. 
Proteid  food,  146. 
Proteids,  145;  importance  of,  145. 

Vegetable,  147. 

Protoplasm,  4;  animal,  202;  vegetal,  202. 
Ptyalin,  168,  176. 
Puff-balls,  121. 
Pulmonary  arterv,  42 ;  veins,  42,  43. 

Capillaries,  86. 
Pulp-cavity,  163,  164. 
Pulse,  40. 

Punishment,  by  nature,  227. 
Pupil,  288,  289. 
Putrefaction,  bacteria  of,  127. 
Pylorus,  175. 

Quality  of  voice,  312. 

Quantity  of  blood  in  organs,  75. 

Rabbit,  muscles  of  leg,  9. 

Nerves  of  leg,  9. 
Radiation  of  heat,  137. 
Radius,  332,  333. 
Rainwater,  150. 
Raspberries,  189. 
Rate  of  blood-flo\v,  59. 

Of  heart  beat,  39. 

Of  respiration,  95. 
Reaction  of  blood,  75. 

Time,  262. 

Reading  in   convalescence,  298 ;    heavy 
books,  296;  mornings,  297;  even- 
ings, 297 ;  outdoors,  296. 
Receptacle  of  chyle,  186. 
Rectum,  188. 

Reference  in  sensation,  282. 
Reflex  action,  30,  32,  263. 

Essentials  of,  32. 

And  habit,  267. 

Importance  of,  32. 

Of  spinal  cord  of  frog,  30. 
Refracting  media  of  eye,  289. 
Regulation  of  blood-flow,  68,  69,  107. 

Of  hearl  beat,  66,  67. 

Of  lymph-flow,  77. 


INDEX. 


Regulation  of  respiration,  99,  108. 

Of  temperature,  136. 
Renal  arteries,  44;  veins,  44. 
Renewal  of  blood  and  lymph,  200. 
Rennet,  174. 
Rennin,  174. 

Repose,  effeet  on  digestion,  192. 
Reserve  air,  97. 
Residual  air,  97. 
Respiration,  abdominal,  95. 

And  candle,  201. 

Chemistry  of,  100. 

Control  of,  99. 

Forced,  94. 

Modifications  of,  95. 

Movements  of,  91. 

Organs  of,  84. 

And  oxidation,  201. 

Rate  of,  95. 

Thoracic,  95. 

Respiratory  center,  99  ;  sounds,  99. 
Rest  of  brain,  246,  247. 

Of  eyes,  297. 

Of  heart,  48. 

Usefulness  of,  268. 
Restoring  breathing,  320. 
Resuscitation  from  carbon  dioxid,  322. 

From  drowning,  317. 
Retina,  287,  292,  293. 
Rhubarb,  189. 

Ribs,  332,  333;  in  respiration,  92. 
Rice,  149,  189. 
Rickets,  339. 
Rigor  mortis,  346. 
Ring,  neural,  330. 
River  and  blood-flow,  195. 
Roasting  meat,  156. 
Rods  and  cones,  293,  292. 
Roots  of  spinal  nerves,  26,  29,  31. 
Running,  20. 
Rye,  149. 

Sacrum,  333,  334,  335. 

Sago,  189. 

Salines,  302. 

Saliva,  amount  of,  168;  uses  of,  168. 

Salivary  glands,  166,  186. 

Salted  meat,  189. 

Salts,  153. 

Satiety,  272. 


Scapula,  332,  333. 
Sciatic  nerve  of  frog,  9. 
Sclerotic  coat,  287,  288. 
Sculpture  and  anatomy,  346. 
Semicircular  canals,  305,  306. 
Semilunar  valves,  42. 
Sensation  centers,  243,  245 

Defined,  265. 

Nature  of,  264. 

And  stimulus,  262. 
Sensations  and  brain,  30. 

Of  color,  294. 

Common,  272. 

Cutaneous,  278. 

General,  271. 

Lingering,  267. 

Referred  to  nerve  ends,  282. 

Relative,  265. 

Subjective,  265. 
Sense  of  equilibrium,  306. 

Of  hearing,  304. 

Muscular,  272. 

Of  sight,  285. 

Of  smell,  303. 

Of  taste,  301. 

Temperature,  283. 

Of  touch,  279. 

Senses,  classification  of,  271. 
Serous  cavities,  80. 
Sewer  and  water  pipes,  199. 
Sheath,  medullary,  27. 

Of  muscle  fiber,  u,  12. 

Of  nerve  fiber,  28. 
Sick,  care  of,  325  ;  food  for,  327. 
Sickroom,  324. 

Sweeping,  125,  327. 

Temperature  of,  325. 
Sighing,  95. 
Sight,  285. 

Sigmoid  flexure,  188. 
Sign,  local,  281. 
Skeleton,  330. 

Appendicular,  330. 

Axial,  330. 

Cavities  of,  337. 
Skeleton,  side  view  of,  332. 
Skin,  color  of,  132. 

Functions  of,  130,  136. 

And  kidneys,  141. 

Papilla;  of,  279. 


INDEX. 


Skin,  structure  of,  130. 

Skull,  332,  333. 

Sleeplessness,  246. 

Small  intestine,  160. 

Smell,  303. 

Smoked  meat,  189. 

Snake  bites,  324. 

Sneezing,  95  ;  prevention  of,  328. 

Sniffing,  95,  304. 

Snoring,  95. 

Sobbing,  95. 

Socket-joint,  339. 

Soft  palate,  160. 

Solar  plexus,  66. 

Sound,  306. 

Sounds  of  heart,  49. 

Respiratory,  99. 
Soup,  156;  value  of,  191. 
Special  senses,  271,  278. 
Specific  gravity  of  blood,  75. 
Speech  center,  245,  264. 

And  voice,  312. 
Sphenoid  bone,  333. 
Sphincter  muscles,  175. 
Spices,  189. 
Spinach,  189. 
Spinal  bulb,  236,  245,  246. 
Spinal  column,  334;  flexibility  of,  335. 
Spinal  cord,  24. 

Cross  section  of,  28. 

Figure  of,  29. 

Functions  of,  29. 

Reflex  action  of,  30. 
Spinal  nerves,  26. 

Roots  of,  26,  29. 

Effect  of  severing,  34. 
Spine,  curvature  of,  339. 
Spinous  process,  331. 
Spirillum,  of  Asiatic  cholera,  123. 
Spitting,  96. 
Spleen,  81. 
Spot,  blind,  293. 

Yellow,  288. 

Spots,  cold,  283 ;  warm,  283. 
Sprains,  339. 
Squash,  189. 
Standing,  19. 
Stapes,  333. 
Starch,  189. 
Starvation  of  cells,  200. 


Starvation  of  nervous  system,  247. 

Steapsin,  179. 

Stereoscopic  vision,  295. 

Sternum,  332,  333. 

Stiffened  joints,  340. 

Stimulants,  210, 212 ;  in  resuscitation, 320. 

Stimulating  nerve  roots,  34. 

Spinal  nerves,  33. 
Stimuli  of  nerves,  261. 
Stimulus  and  sensation,  262. 
Stings  of  bees,  324. 
Stirrup  bones,  333. 
Stomach,  160,  172,  186. 

Absorption  from,  175. 

Blood-supply  of,  173. 

Coats  of,  172. 

Churning,  174. 

Digestion,  time  of,  175. 

Hemorrhage  of,  315. 

Position,  85,  160,  172,  186. 

Structure  of,  172. 
Storage  of  oxygen,  no. 
Stove,  116;  with  jacket,  117. 
Strength  of  light,  297. 

Source  of,  14. 
Structure  of  artery,  51. 

Of  bone,  18,  337. 

Of  brain,  238,  239,  241. 

Of  eye,  288. 

Of  gullet,  171. 

Of  heart,  41. 

Of  kidney,  139,  140. 

Of  larynx,  310. 

Of  muscle,  10,  n. 

Of  nerves,  27. 

Of  retina,  292. 

Of  skin,  130. 
Structure  of  stomach,  172;  of  tooth,  163, 

164. 

Subclavian  vein,  44,  186. 
Subjective  sensations,  265. 
Sublingual  salivary  gland,  166,  186. 
Submaxillary  salivary  gland,  166,  186. 
Sucking,  96. 

Suffocation  in  wells,  322. 
Sugar,  144 ;  cane,  179 ;  grape,  179. 

In  diabetes,  199. 
Sunshine,  139. 
Sunstroke,  317. 
Supination,  337. 


INDEX. 


Suspensory  ligament,  288. 

Swallowing,  171 ;  and  breathing,  170, 171. 

Sweat,  130. 

Composition  of,  135. 

Evaporation  of,  137. 

Glands,  130,  133,  135. 

Pores,  130. 
Sweeping,  125. 

Sickroom,  125,  327. 
Sweetmeats,  191. 
Sweets,  where  tasted,  302. 
Swimming,  321. 

Sympathetic  nervous  system,  65,  66. 
Sympathy  between  eyes,  294. 

In  nursing,  325. 
Synovia,  19. 
Systole,  47. 

Table  of  bones,  333. 

Tapioca,  189. 

Tarsal  bones,  333. 

Tarsus,  332,  333. 

Taste,  301. 

Tasting,  conditions  of,  302. 

Tea,  154,  189,  212 ;  beef,  155. 

Tears,  286. 

Teeth,  162,  163. 

Arrangement  of,  164. 

Care  of,  166. 

Kinds,  164. 

Milk,  164. 

Temperance  drinks,  211. 
Temperature  of  body,  108. 
Temperature,  regulation  of,  136. 

Sense,  283. 

Of  sickroom,  325. 

Effect  on  taste,  302. 
Temporal  bone,  332, 333 ;  muscle,  9. 
Tendinous  cords,  41,  46. 
Tendon,  7,  10,  n,  15. 
Tennis,  228. 
Tetanus,  35. 
Thein,  154. 
Theobromin,  155. 
Thermometer  in  sickroom,  325. 
Thigh,  wounds  in,  315. 
Thirst,  276,  272. 
Thoracic  duct,  183. 

Respiration,  95. 

Vertebra,  331,  335. 


Thorax,  cross  section  of,  89. 

Thorns,  wounds  from,  323. 

Thyroid  cartilage,  309. 

Tibia,  332,  333. 

Tidal  air,  97. 

Time  for  bathing,  233 ;  of  eating,  193. 

Tissue  defined,  3. 

Connective,  n,  12. 

Fatty,  201. 

Tissues,  oxidation  of,  107. 
Tobacco,  258. 
Tomatoes,  189. 
Tongue,  162. 

Nerves  of,  301. 

Papillae  of,  301. 
Tooth,  structure  of,  163,  164. 
Touch,  sense  of,  279. 

Corpuscles  of,  279. 
Trachea,  43,  86. 
Training  and  alcohol,  209. 
Transfusion  of  blood,  81. 
Transmission  of  nerve  impulse,  36. 
Treatment  of  burns,  316. 

Of  the  drowned,  317. 

Of  fainting,  316. 

In  poisoning,  322,  347. 
Triceps  muscle,  8. 
Tricuspid  valve,  41. 
Trigeminal  nerve,  237. 
Trophic  nerves,  251. 
Trypsin,  178. 
Tube,  digestive,  159. 

Eustachian,  305,  306. 
Tubes,  lymph,  76. 
Tuberculosis,  bacillus  of,  123. 
Turbinated  bones,  333. 
Typhoid  fever,  151 ;  bacillus  of,  123. 

Ulna,  332, 333. 

Upsetting  of  boats,  321. 

Urea,  139;  and  muscular  exertion,  202. 

Uses  of  bones,  330. 

Utilization  of  energy,  205. 

Uvula,  160. 

Vagus  nerves,  66,  239. 

Valve,  mitral,  41 ;  tricuspid,  41. 

Valves  of  heart,  41. 

Of  lymph  tubes,  76. 

Semilunar,  42,  46. 


386 


INDEX. 


Valves  of  veins,  57. 
Variation  of  blood-supply,  50. 
Vaso-constrictor  nerves,  67. 

-dilator  nerves,  67. 

-motor  nerves,  68. 
Vegetable  proteid,  147. 
Vegetables,  149. 
Vegetal  protoplasm,  202. 
Vegetarians,  154. 
Veins,  57. 

Bleeding  from,  315. 

Distribution  of,  44. 

Flow  in,  61. 

Hepatic,  177,  186. 

Iliac,  44. 

Jugular,  44. 

Mesenteric,  186. 

Portal,  177. 

Postcaval,  42,  44,  177,  186. 

Precaval,  42,  44,  186. 

Effect  of  pressure  on,  58. 

Pulmonary,  42,  43. 

Renal,  44. 

Subclavian,  44,  286. 

Valves  in,  57. 
Ventilating  flues,  115. 
Ventilation,  need  of,  114. 

Principles  of,  115. 
Ventricle,  contraction  of,  46. 

Dilation  of,  47. 

Of  heart,  41. 

Vermiform  appendix,  187. 
Vertebra,  articulations  of,  335. 

Parts  of,  330. 

Processes  of,  330. 
Vertebrae,  cervical, -332,  333,  334. 

Lumbar,  335. 

Thoracic,  331,  332,  333,  335. 
Vesicles,  air,  84. 
Villi,  179,  181,  184,  185. 
Vision,  stereoscopic,  295. 
Visual  center,  264. 
Vital  capacity,  97. 
Vitreous  humor,  288,  289. 
Vocal  cords,  309. 
Voice,  309. 

Change  of,  313. 

Culture  of,  313. 

I^oudness  of,  311. 

Pitch  of,  312. 


Voice,  quality  of,  312. 

And  speech,  312. 
Volition,  242,  243. 
Voluntary  inhibition.  35. 
Vomer,  333. 
Yourls  and  consonants,  312. 


\Yalking,  20;  in  sickroom,  327. 
Warm  baths,  233. 

Spots,  283. 

Watching  in  sickroom,  326. 
Water,  150. 

Boiling,  152. 

Drinking,  152. 

Ice,  152. 

Impurities  in,  151, 

Rain,  150. 

Well,  150. 

Water-cushion  of  brain,  248. 
Water-pipes  and  bloodstream,  199. 

And  sewer,  199. 
Wearing  glasses,  299. 
Web  of  frog's  foot,  52,  53. 
Weight  of  bones,  337. 

In  levers,  16. 
Well-water,  150. 
Wheat,  148. 

Flour,  148. 

Whispering,  313  ;  in  sickroom,  327. 
Whistling,  96. 
White  matter  of  brain,  241. 

Circulation  in,  249. 

Of  spinal  cord,  28,  29. 
Wild  game,  189. 
Wind,  116. 

Windows,  double,  119. 
Windpipe,  86. 
Work  of  blood,  39. 

Brain,  246. 

Of  heart,  48. 
Worker,  outdoor,  2. 

Wounds  from    rusty  nails,  323;     from 
thorns,  323. 

In  thigh,  315. 


Yawning,  95. 
Yeast,  121. 
Yellow  spot,  288. 


BIOLOGY 
/    LIBRARY 

G 

UNIVERSITY  OF  CALIFORNIA  LIBRARY 


